Easy to manufacture autoclavable led for optical tracking

ABSTRACT

An optical tracking system is provided. The optical tracking system comprises an autoclavable fiducial marker assembly including an opaque housing, a light source, a window panel configured to refract light rays from the light source therethrough, and a metallized coating forming a hermetic seal at an interface of the window panel and the opaque housing. The fiducial marker assembly is configured to shield a peripheral edge of the window panel from the light rays. The system further comprises a tracking device comprising at least two optical sensors configured to detect a position of a light ray emitted by the light source. The system further comprises a processor configured to receive the position of the light rays from the optical sensors, shift the position of each light ray based on a calculated refraction deviation, and triangulate the location of the light source based on the shifted position of each light ray.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 63/049,319 entitled “Easy to Manufacture AutoclavableLED for Optical Tracking,” filed Jul. 8, 2020, which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to methods, systems, andapparatuses for optical tracking. The disclosed techniques may beapplied to, for example, shoulder, hip, and knee arthroplasties, as wellas other surgical interventions such as arthroscopic procedures, spinalprocedures, maxillofacial procedures, rotator cuff procedures, ligamentrepair and replacement procedures. More particularly, the presentdisclosure relates to systems and apparatuses comprising an autoclavableLED marker configured to facilitate optical tracking with highlocalization accuracy.

BACKGROUND

Optical tracking is commonly used in computer assisted surgery (CAS)applications to assist physicians in localizing and navigating withrespect to targeted tissues and treating the targeted tissues. Fiducialmarkers may be coupled to an object of interest and serve as opticalreferences to be tracked by the system. In some applications, fiducialmarkers comprise light emitting diodes (LEDs) that emit light to betracked by an optical tracking device of the system, e.g., a camera. Thesystem determines the location of the object of interest based oncontinuous monitoring of the emitted light.

The fiducial markers, which are generally packaged independently andcoupled to a housing or support, may be designed for long-term use andre-use in surgical settings. However, in order to be used in thismanner, the fiducial markers must be designed to withstand autoclavecycles in order to meet the sterilization requirements of the operatingroom environment. While designs for sealed autoclavable LEDs have beenproposed (see for example, DE 10 2015 103 331 B4 and DE 20 2010 000 518U1), encapsulation of the light source often results in undesirableoptical effects. Generally, designing autoclavable LEDs for opticaltracking has been difficult without sacrificing metrological accuracy.

Referring now to FIG. 8 , a two-dimensional illustration of a sealedlight source and the resulting localization error is depicted. Afiducial marker 800 may comprise a housing 805, an exit window 810, anda light source 815 and may be used in conjunction with a stereo opticaltracking device 820 comprising optical sensors 825 to triangulate thelocation of the light source 815. However, when light rays 830 areemitted by the light source 815, they may undergo refraction 830A asthey pass through the exit window 810 before the exiting light rays 830Breach the optical sensors 825. As such, the light rays 830 do not formcontinuous straight lines and the amount of refraction 830A also variesbased on the optical properties of the exit window 810 and the tiltangulation of the fiducial marker 800 with respect to each opticalsensor 825. Where the system assumes the light rays 830 as straightlines 835, the computed location 840 of the light source 815 may be offby a significant margin from the true location. Accordingly, largemetrological errors in the computation may result in unacceptablelocalization inaccuracy.

Current solutions include fiducial markers designed to mitigaterefraction. For example, U.S. Pat. No. 7,147,352 proposes a light sourcelocated at a spherical center of a domed exit window such that lightrays are substantially normal to the exit window in all directions.However, such designs require construction with a very high level ofaccuracy beyond the mechanical tolerance of standard manufacturingtechniques. Manufacturing fiducial markers with the requisite level ofaccuracy to reduce localization error requires complex manufacturing andassembly techniques that lead to very high fabrication costs.

As such, it would be advantageous to have an autoclavable LED that isconducive to simple manufacturing techniques and reduced localizationinaccuracy. Further, it would be advantageous to have a systemconfigured to reduce metrological errors associated with lightrefraction.

SUMMARY

An optical tracking system is provided. The optical tracking systemcomprises an autoclavable fiducial marker assembly comprising: an opaquehousing defining an interior cavity, a light emitting semiconductor diedisposed in the interior cavity and in electrical communication with ananode and a cathode, a window panel joined to the opaque housing toenclose the interior cavity between the window panel and the opaquehousing, the window panel configured to refract a plurality of lightrays emitted by the light emitting semiconductor die, and a metallizedcoating forming a hermetic seal at an interface of the window panel andthe opaque housing, wherein the fiducial marker assembly is configuredto shield a peripheral edge of the window panel from the plurality oflight rays; a tracking device comprising at least two optical sensors,each optical sensor configured to detect a position of a light ray ofthe plurality of light rays; a processor; and a non-transitory,computer-readable medium storing instructions that, when executed, causethe processor to: receive the position of each light ray from eachoptical sensor, shift the position of each light ray based on acalculated refraction deviation, and triangulate the location of thelight emitting semiconductor die based on the shifted position of eachlight ray.

According to some embodiments, the calculated refraction deviation isbased on a known refraction index of the window panel, a known thicknessof the window panel, and an orientation of the fiducial marker assemblywith respect to each optical sensor. According to additionalembodiments, the tracking device is configured to detect imageinformation related to the orientation of the fiducial marker. Accordingto additional embodiments, the optical tracking system further comprisesan accelerometer configured to detect and transmit orientationinformation related to the orientation of the fiducial marker.

According to some embodiments, the metallized coating forms a ringextending radially inward from the interface to cover a portion of thewindow panel, wherein the ring is configured to shield the peripheraledge of the window panel from the plurality of light rays.

According to some embodiments, the metallized coating comprises solder.

According to some embodiments, the anode and the cathode extend throughthe opaque housing.

According to some embodiments, the opaque housing defines a notchconfigured to receive the window panel.

According to some embodiments, the window panel defines a notchconfigured to secure the light emitting diode within a marker support.

According to some embodiments, the fiducial marker assembly furthercomprises a rod supporting the light emitting semiconductor dieproximate the window panel. According to additional embodiments, the rodcomprises a heat sink configured to discharge heat from the lightemitting semiconductor die. According to additional embodiments, adiameter of the light emitting semiconductor die is greater than orequal to a diameter of the rod. According to additional embodiments, athermal expansion coefficient of each of the opaque housing, the windowpanel, and the rod are substantially equal. According to additionalembodiments, the opaque housing comprises a nickel-cobalt ferrous alloy;the window panel comprises an aluminum oxide; and the rod comprises anickel-cobalt ferrous alloy.

According to some embodiments, the window panel comprises alight-absorbing layer affixed on an interior face of the window panelfacing the metallized coating.

An autoclavable fiducial marker assembly is also provided. The fiducialmarker assembly comprises an opaque housing defining an interior cavity;a light emitting semiconductor die disposed in the interior cavity andin electrical communication with an anode and a cathode; a window paneljoined to the opaque housing to enclose the interior cavity between thewindow panel and the opaque housing, the window panel configured torefract a plurality of light rays emitted by the light emittingsemiconductor die; and a metallized coating forming a hermetic seal atan interface of the window panel and the opaque housing, wherein thefiducial marker assembly is configured to shield a peripheral edge ofthe window panel from the plurality of light rays.

According to some embodiments, the metallized coating forms a ringextending radially inward from the interface to cover a portion of thewindow panel, wherein the ring is configured to shield the peripheraledge of the window panel from the plurality of light rays.

According to some embodiments, the metallized coating comprises solder.

According to some embodiments, the anode and the cathode extend throughthe opaque housing.

According to some embodiments, the opaque housing defines a notchconfigured to receive the window panel.

According to some embodiments, the window panel defines a notchconfigured to secure the light emitting diode within a marker support.

According to some embodiments, the fiducial marker assembly furthercomprises a rod supporting the light emitting semiconductor dieproximate the window panel. According to additional embodiments, the rodcomprises a heat sink configured to discharge heat from the lightemitting semiconductor die. According to additional embodiments, adiameter of light emitting semiconductor die is greater than or equal toa diameter of the rod. According to additional embodiments, the rodcomprises a nickel-cobalt ferrous alloy. According to additionalembodiments, a thermal expansion coefficient of each of the opaquehousing, the window panel, and the rod are substantially equal.

According to some embodiments, the window panel comprises alight-absorbing layer affixed on an interior face of the window panelfacing the metallized coating.

According to some embodiments, the window panel comprises an aluminumoxide.

According to some embodiments, the opaque housing comprises anickel-cobalt ferrous alloy.

A method of tracking an object is also provided. The method comprisescoupling a fiducial marker assembly to the object, wherein the fiducialmarker assembly comprises: an opaque housing defining an interiorcavity, a light emitting semiconductor die disposed in the interiorcavity and in electrical communication with an anode and a cathode, awindow panel joined to the opaque housing to enclose the interior cavitybetween the window panel and the opaque housing, the window panelconfigured to refract a plurality of light rays emitted by the lightemitting semiconductor die, and a metallized coating forming a hermeticseal at an interface of the window panel and the opaque housing, whereinthe fiducial marker assembly is configured to shield a peripheral edgeof the window panel from the plurality of light rays; detecting, by eachof two or more optical sensors, a position of a light ray of theplurality of light rays; receiving, by a processor, the detectedposition of the light ray from each of the two or more optical sensors;adjusting, by the processor, the detected position of each light rayfrom each of the two or more optical sensors based on a refractiondeviation to obtain an adjusted position of each light ray;triangulating, by the computing device, the location of the lightemitting semiconductor die from the adjusted position of each light ray;and calculating, by the computing device, the location of the objectbased on a known spatial relationship between the object and the lightemitting semiconductor die.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate the embodiments of the invention andtogether with the written description serve to explain the principles,characteristics, and features of the invention. In the drawings:

FIG. 1 depicts an operating theatre including an illustrativecomputer-assisted surgical system (CASS) in accordance with anembodiment.

FIG. 2 depicts an example of an electromagnetic sensor device accordingto some embodiments.

FIG. 3A depicts an alternative example of an electromagnetic sensordevice, with three perpendicular coils, according to some embodiments.

FIG. 3B depicts an alternative example of an electromagnetic sensordevice, with two nonparallel, affixed coils, according to someembodiments.

FIG. 3C depicts an alternative example of an electromagnetic sensordevice, with two nonparallel, separate coils, according to someembodiments.

FIG. 4 depicts an example of electromagnetic sensor devices and apatient bone according to some embodiments

FIG. 5A depicts illustrative control instructions that a surgicalcomputer provides to other components of a CASS in accordance with anembodiment.

FIG. 5B depicts illustrative control instructions that components of aCASS provide to a surgical computer in accordance with an embodiment.

FIG. 5C depicts an illustrative implementation in which a surgicalcomputer is connected to a surgical data server via a network inaccordance with an embodiment.

FIG. 6 depicts an operative patient care system and illustrative datasources in accordance with an embodiment.

FIG. 7A depicts an illustrative flow diagram for determining apre-operative surgical plan in accordance with an embodiment.

FIG. 7B depicts an illustrative flow diagram for determining an episodeof care including pre-operative, intraoperative, and post-operativeactions in accordance with an embodiment.

FIG. 7C depicts illustrative graphical user interfaces including imagesdepicting an implant placement in accordance with an embodiment.

FIG. 8 depicts an illustrative sealed light source and typicallocalization error in accordance with an embodiment.

FIGS. 9A-9B depict an illustrative fiducial marker for tracking anobject during a surgical procedure in accordance with an embodiment.

FIG. 10 depicts an alternate fiducial marker for tracking an objectduring a surgical procedure in accordance with an embodiment.

FIGS. 11A-11B depict an alternate fiducial marker for tracking an objectduring a surgical procedure in accordance with an embodiment.

FIG. 12 depicts a block diagram of an illustrative system for trackingan object in accordance with an embodiment.

FIG. 13 depicts an illustrative computation of the location of a lightsource with refraction correct in accordance with an embodiment.

FIGS. 14A-14C depict an exemplary evaluation of localization error inaccordance with an embodiment.

FIG. 15 depicts a flow diagram of an illustrative method of tracking anobject with a fiducial marker in accordance with an embodiment.

FIG. 16 illustrates a block diagram of an illustrative data processingsystem in which embodiments are implemented.

DETAILED DESCRIPTION

This disclosure is not limited to the particular systems, devices andmethods described, as these may vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only and is not intended to limit the scope.

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. Nothing in this disclosure is to be construed as anadmission that the embodiments described in this disclosure are notentitled to antedate such disclosure by virtue of prior invention. Asused in this document, the term “comprising” means “including, but notlimited to.”

Definitions

For the purposes of this disclosure, the term “implant” is used to referto a prosthetic device or structure manufactured to replace or enhance abiological structure. For example, in a total hip replacement procedurea prosthetic acetabular cup (implant) is used to replace or enhance apatients worn or damaged acetabulum. While the term “implant” isgenerally considered to denote a man-made structure (as contrasted witha transplant), for the purposes of this specification an implant caninclude a biological tissue or material transplanted to replace orenhance a biological structure.

For the purposes of this disclosure, the term “real-time” is used torefer to calculations or operations performed on-the-fly as events occuror input is received by the operable system. However, the use of theterm “real-time” is not intended to preclude operations that cause somelatency between input and response, so long as the latency is anunintended consequence induced by the performance characteristics of themachine.

Although much of this disclosure refers to surgeons or other medicalprofessionals by specific job title or role, nothing in this disclosureis intended to be limited to a specific job title or function. Surgeonsor medical professionals can include any doctor, nurse, medicalprofessional, or technician. Any of these terms or job titles can beused interchangeably with the user of the systems disclosed hereinunless otherwise explicitly demarcated. For example, a reference to asurgeon also could apply, in some embodiments to a technician or nurse.

The systems, methods, and devices disclosed herein are particularly welladapted for surgical procedures that utilize surgical navigationsystems, such as the NAVIO® surgical navigation system. NAVIO is aregistered trademark of BLUE BELT TECHNOLOGIES, INC. of Pittsburgh, Pa.,which is a subsidiary of SMITH & NEPHEW, INC. of Memphis, Tenn.

CASS Ecosystem Overview

FIG. 1 provides an illustration of an example computer-assisted surgicalsystem (CASS) 100, according to some embodiments. As described infurther detail in the sections that follow, the CASS uses computers,robotics, and imaging technology to aid surgeons in performingorthopedic surgery procedures such as total knee arthroplasty (TKA) ortotal hip arthroplasty (THA). For example, surgical navigation systemscan aid surgeons in locating patient anatomical structures, guidingsurgical instruments, and implanting medical devices with a high degreeof accuracy. Surgical navigation systems such as the CASS 100 oftenemploy various forms of computing technology to perform a wide varietyof standard and minimally invasive surgical procedures and techniques.Moreover, these systems allow surgeons to more accurately plan, trackand navigate the placement of instruments and implants relative to thebody of a patient, as well as conduct pre-operative and intra-operativebody imaging.

An Effector Platform 105 positions surgical tools relative to a patientduring surgery. The exact components of the Effector Platform 105 willvary, depending on the embodiment employed. For example, for a kneesurgery, the Effector Platform 105 may include an End Effector 105B thatholds surgical tools or instruments during their use. The End Effector105B may be a handheld device or instrument used by the surgeon (e.g., aNAVIO® hand piece or a cutting guide or jig) or, alternatively, the EndEffector 105B can include a device or instrument held or positioned by aRobotic Arm 105A. While one Robotic Arm 105A is illustrated in FIG. 1 ,in some embodiments there may be multiple devices. As examples, theremay be one Robotic Arm 105A on each side of an operating table T or twodevices on one side of the table T. The Robotic Arm 105A may be mounteddirectly to the table T, be located next to the table T on a floorplatform (not shown), mounted on a floor-to-ceiling pole, or mounted ona wall or ceiling of an operating room. The floor platform may be fixedor moveable. In one particular embodiment, the robotic arm 105A ismounted on a floor-to-ceiling pole located between the patient's legs orfeet. In some embodiments, the End Effector 105B may include a sutureholder or a stapler to assist in closing wounds. Further, in the case oftwo robotic arms 105A, the surgical computer 150 can drive the roboticarms 105A to work together to suture the wound at closure.Alternatively, the surgical computer 150 can drive one or more roboticarms 105A to staple the wound at closure.

The Effector Platform 105 can include a Limb Positioner 105C forpositioning the patient's limbs during surgery. One example of a LimbPositioner 105C is the SMITH AND NEPHEW SPIDER2 system. The LimbPositioner 105C may be operated manually by the surgeon or alternativelychange limb positions based on instructions received from the SurgicalComputer 150 (described below). While one Limb Positioner 105C isillustrated in FIG. 1 , in some embodiments there may be multipledevices. As examples, there may be one Limb Positioner 105C on each sideof the operating table T or two devices on one side of the table T. TheLimb Positioner 105C may be mounted directly to the table T, be locatednext to the table T on a floor platform (not shown), mounted on a pole,or mounted on a wall or ceiling of an operating room. In someembodiments, the Limb Positioner 105C can be used in non-conventionalways, such as a retractor or specific bone holder. The Limb Positioner105C may include, as examples, an ankle boot, a soft tissue clamp, abone clamp, or a soft-tissue retractor spoon, such as a hooked, curved,or angled blade. In some embodiments, the Limb Positioner 105C mayinclude a suture holder to assist in closing wounds.

The Effector Platform 105 may include tools, such as a screwdriver,light or laser, to indicate an axis or plane, bubble level, pin driver,pin puller, plane checker, pointer, finger, or some combination thereof.

Resection Equipment 110 (not shown in FIG. 1 ) performs bone or tissueresection using, for example, mechanical, ultrasonic, or lasertechniques. Examples of Resection Equipment 110 include drillingdevices, burring devices, oscillatory sawing devices, vibratoryimpaction devices, reamers, ultrasonic bone cutting devices, radiofrequency ablation devices, reciprocating devices (such as a rasp orbroach), and laser ablation systems. In some embodiments, the ResectionEquipment 110 is held and operated by the surgeon during surgery. Inother embodiments, the Effector Platform 105 may be used to hold theResection Equipment 110 during use.

The Effector Platform 105 also can include a cutting guide or jig 105Dthat is used to guide saws or drills used to resect tissue duringsurgery. Such cutting guides 105D can be formed integrally as part ofthe Effector Platform 105 or Robotic Arm 105A, or cutting guides can beseparate structures that can be matingly and/or removably attached tothe Effector Platform 105 or Robotic Arm 105A. The Effector Platform 105or Robotic Arm 105A can be controlled by the CASS 100 to position acutting guide or jig 105D adjacent to the patient's anatomy inaccordance with a pre-operatively or intraoperatively developed surgicalplan such that the cutting guide or jig will produce a precise bone cutin accordance with the surgical plan.

The Tracking System 115 uses one or more sensors to collect real-timeposition data that locates the patient's anatomy and surgicalinstruments. For example, for TKA procedures, the Tracking System mayprovide a location and orientation of the End Effector 105B during theprocedure. In addition to positional data, data from the Tracking System115 also can be used to infer velocity/acceleration ofanatomy/instrumentation, which can be used for tool control. In someembodiments, the Tracking System 115 may use a tracker array attached tothe End Effector 105B to determine the location and orientation of theEnd Effector 105B. The position of the End Effector 105B may be inferredbased on the position and orientation of the Tracking System 115 and aknown relationship in three-dimensional space between the TrackingSystem 115 and the End Effector 105B. Various types of tracking systemsmay be used in various embodiments of the present invention including,without limitation, Infrared (IR) tracking systems, electromagnetic (EM)tracking systems, video or image based tracking systems, and ultrasoundregistration and tracking systems. Using the data provided by thetracking system 115, the surgical computer 150 can detect objects andprevent collision. For example, the surgical computer 150 can preventthe Robotic Arm 105A and/or the End Effector 105B from colliding withsoft tissue.

Any suitable tracking system can be used for tracking surgical objectsand patient anatomy in the surgical theatre. For example, a combinationof IR and visible light cameras can be used in an array. Variousillumination sources, such as an IR LED light source, can illuminate thescene allowing three-dimensional imaging to occur. In some embodiments,this can include stereoscopic, tri-scopic, quad-scopic, etc. imaging. Inaddition to the camera array, which in some embodiments is affixed to acart, additional cameras can be placed throughout the surgical theatre.For example, handheld tools or headsets worn by operators/surgeons caninclude imaging capability that communicates images back to a centralprocessor to correlate those images with images captured by the cameraarray. This can give a more robust image of the environment for modelingusing multiple perspectives. Furthermore, some imaging devices may be ofsuitable resolution or have a suitable perspective on the scene to pickup information stored in quick response (QR) codes or barcodes. This canbe helpful in identifying specific objects not manually registered withthe system. In some embodiments, the camera may be mounted on theRobotic Arm 105A.

Although, as discussed herein, the majority of tracking and/ornavigation techniques utilize image-based tracking systems (e.g., IRtracking systems, video or image based tracking systems, etc.). However,electromagnetic (EM) based tracking systems are becoming more common fora variety of reasons. For example, implantation of standard opticaltrackers requires tissue resection (e.g., down to the cortex) as well assubsequent drilling and driving of cortical pins. Additionally, becauseoptical trackers require a direct line of sight with a tracking system,the placement of such trackers may need to be far from the surgical siteto ensure they do not restrict the movement of a surgeon or medicalprofessional.

Generally, EM based tracking devices include one or more wire coils anda reference field generator. The one or more wire coils may be energized(e.g., via a wired or wireless power supply). Once energized, the coilcreates an electromagnetic field that can be detected and measured(e.g., by the reference field generator or an additional device) in amanner that allows for the location and orientation of the one or morewire coils to be determined. As should be understood by someone ofordinary skill in the art, a single coil, such as is shown in FIG. 2 ,is limited to detecting five (5) total degrees-of-freedom (DOF). Forexample, sensor 200 may be able to track/determine movement in the X, Y,or Z direction, as well as rotation around the Y-axis 202 or Z-axis 201.However, because of the electromagnetic properties of a coil, it is notpossible to properly track rotational movement around the X axis.

Accordingly, in most electromagnetic tracking applications, a three coilsystem, such as that shown in FIG. 3A is used to enable tracking in allsix degrees of freedom that are possible for a rigid body moving in athree-dimensional space (i.e., forward/backward 310, up/down 320,left/right 330, roll 340, pitch 350, and yaw 360). However, theinclusion of two additional coils and the 90° offset angles at whichthey are positioned may require the tracking device to be much larger.Alternatively, as one of skill in the art would know, less than threefull coils may be used to track all 6DOF. In some EM based trackingdevices, two coils may be affixed to each other, such as is shown inFIG. 3B. Because the two coils 301B and 302B are rigidly affixed to eachother, not perfectly parallel, and have locations that are knownrelative to each other, it is possible to determine the sixth degree offreedom 303B with this arrangement.

Although the use of two affixed coils (e.g., 301B and 302B) allows forEM based tracking in 6DOF, the sensor device is substantially larger indiameter than a single coil because of the additional coil. Thus, thepractical application of using an EM based tracking system in a surgicalenvironment may require tissue resection and drilling of a portion ofthe patient bone to allow for insertion of a EM tracker. Alternatively,in some embodiments, it may be possible to implant/insert a single coil,or 5DOF EM tracking device, into a patient bone using only a pin (e.g.,without the need to drill or carve out substantial bone).

Thus, as described herein, a solution is needed for which the use of anEM tracking system can be restricted to devices small enough to beinserted/embedded using a small diameter needle or pin (i.e., withoutthe need to create a new incision or large diameter opening in thebone). Accordingly, in some embodiments, a second 5DOF sensor, which isnot attached to the first, and thus has a small diameter, may be used totrack all 6DOF. Referring now to FIG. 3C, in some embodiments, two 5DOFEM sensors (e.g., 301C and 302C) may be inserted into the patient (e.g.,in a patient bone) at different locations and with different angularorientations (e.g., angle 303C is non-zero).

Referring now to FIG. 4 , an example embodiment is shown in which afirst 5DOF EM sensor 401 and a second 5DOF EM sensor 402 are insertedinto the patient bone 403 using a standard hollow needle 405 that istypical in most OR(s). In a further embodiment, the first sensor 401 andthe second sensor 402 may have an angle offset of “a” 404. In someembodiments, it may be necessary for the offset angle “a” 404 to begreater than a predetermined value (e.g., a minimum angle of 0.50°,0.75°, etc.). This minimum value may, in some embodiments, be determinedby the CASS and provided to the surgeon or medical professional duringthe surgical plan. In some embodiments, a minimum value may be based onone or more factors, such as, for example, the orientation accuracy ofthe tracking system, a distance between the first and second EM sensors.The location of the field generator, a location of the field detector, atype of EM sensor, a quality of the EM sensor, patient anatomy, and thelike.

Accordingly, as discussed herein, in some embodiments, a pin/needle(e.g., a cannulated mounting needle, etc.) may be used to insert one ormore EM sensors. Generally, the pin/needle would be a disposablecomponent, while the sensors themselves may be reusable. However, itshould be understood that this is only one potential system, and thatvarious other systems may be used in which the pin/needle and/or EMsensors are independently disposable or reusable. In a furtherembodiment, the EM sensors may be affixed to the mounting needle/pin(e.g., using a luer-lock fitting or the like), which can allow for quickassembly and disassembly. In additional embodiments, the EM sensors mayutilize an alternative sleeve and/or anchor system that allows forminimally invasive placement of the sensors.

In another embodiment, the above systems may allow for a multi-sensornavigation system that can detect and correct for field distortions thatplague electromagnetic tracking systems. It should be understood thatfield distortions may result from movement of any ferromagneticmaterials within the reference field. Thus, as one of ordinary skill inthe art would know, a typical OR has a large number of devices (e.g., anoperating table, LCD displays, lighting equipment, imaging systems,surgical instruments, etc.) that may cause interference. Furthermore,field distortions are notoriously difficult to detect. The use ofmultiple EM sensors enables the system to detect field distortionsaccurately, and/or to warn a user that the current position measurementsmay not be accurate. Because the sensors are rigidly fixed to the bonyanatomy (e.g., via the pin/needle), relative measurement of sensorpositions (X, Y, Z) may be used to detect field distortions. By way ofnon-limiting example, in some embodiments, after the EM sensors arefixed to the bone, the relative distance between the two sensors isknown and should remain constant. Thus, any change in this distancecould indicate the presence of a field distortion.

In some embodiments, specific objects can be manually registered by asurgeon with the system preoperatively or intraoperatively. For example,by interacting with a user interface, a surgeon may identify thestarting location for a tool or a bone structure. By tracking fiducialmarks associated with that tool or bone structure, or by using otherconventional image tracking modalities, a processor may track that toolor bone as it moves through the environment in a three-dimensionalmodel.

In some embodiments, certain markers, such as fiducial marks thatidentify individuals, important tools, or bones in the theater mayinclude passive or active identifiers that can be picked up by a cameraor camera array associated with the tracking system. For example, an IRLED can flash a pattern that conveys a unique identifier to the sourceof that pattern, providing a dynamic identification mark. Similarly, oneor two dimensional optical codes (barcode, QR code, etc.) can be affixedto objects in the theater to provide passive identification that canoccur based on image analysis. If these codes are placed asymmetricallyon an object, they also can be used to determine an orientation of anobject by comparing the location of the identifier with the extents ofan object in an image. For example, a QR code may be placed in a cornerof a tool tray, allowing the orientation and identity of that tray to betracked. Other tracking modalities are explained throughout. Forexample, in some embodiments, augmented reality headsets can be worn bysurgeons and other staff to provide additional camera angles andtracking capabilities.

In addition to optical tracking, certain features of objects can betracked by registering physical properties of the object and associatingthem with objects that can be tracked, such as fiducial marks fixed to atool or bone. For example, a surgeon may perform a manual registrationprocess whereby a tracked tool and a tracked bone can be manipulatedrelative to one another. By impinging the tip of the tool against thesurface of the bone, a three-dimensional surface can be mapped for thatbone that is associated with a position and orientation relative to theframe of reference of that fiducial mark. By optically tracking theposition and orientation (pose) of the fiducial mark associated withthat bone, a model of that surface can be tracked with an environmentthrough extrapolation.

The registration process that registers the CASS 100 to the relevantanatomy of the patient also can involve the use of anatomical landmarks,such as landmarks on a bone or cartilage. For example, the CASS 100 caninclude a 3D model of the relevant bone or joint and the surgeon canintraoperatively collect data regarding the location of bony landmarkson the patient's actual bone using a probe that is connected to theCASS. Bony landmarks can include, for example, the medial malleolus andlateral malleolus, the ends of the proximal femur and distal tibia, andthe center of the hip joint. The CASS 100 can compare and register thelocation data of bony landmarks collected by the surgeon with the probewith the location data of the same landmarks in the 3D model.Alternatively, the CASS 100 can construct a 3D model of the bone orjoint without pre-operative image data by using location data of bonylandmarks and the bone surface that are collected by the surgeon using aCASS probe or other means. The registration process also can includedetermining various axes of a joint. For example, for a TKA the surgeoncan use the CASS 100 to determine the anatomical and mechanical axes ofthe femur and tibia. The surgeon and the CASS 100 can identify thecenter of the hip joint by moving the patient's leg in a spiraldirection (i.e., circumduction) so the CASS can determine where thecenter of the hip joint is located.

A Tissue Navigation System 120 (not shown in FIG. 1 ) provides thesurgeon with intraoperative, real-time visualization for the patient'sbone, cartilage, muscle, nervous, and/or vascular tissues surroundingthe surgical area. Examples of systems that may be employed for tissuenavigation include fluorescent imaging systems and ultrasound systems.

The Display 125 provides graphical user interfaces (GUIs) that displayimages collected by the Tissue Navigation System 120 as well otherinformation relevant to the surgery. For example, in one embodiment, theDisplay 125 overlays image information collected from various modalities(e.g., CT, MRI, X-ray, fluorescent, ultrasound, etc.) collectedpre-operatively or intra-operatively to give the surgeon various viewsof the patient's anatomy as well as real-time conditions. The Display125 may include, for example, one or more computer monitors. As analternative or supplement to the Display 125, one or more members of thesurgical staff may wear an Augmented Reality (AR) Head Mounted Device(HMD). For example, in FIG. 1 the Surgeon 111 is wearing an AR HMD 155that may, for example, overlay pre-operative image data on the patientor provide surgical planning suggestions. Various example uses of the ARHMD 155 in surgical procedures are detailed in the sections that follow.

Surgical Computer 150 provides control instructions to variouscomponents of the CASS 100, collects data from those components, andprovides general processing for various data needed during surgery. Insome embodiments, the Surgical Computer 150 is a general purposecomputer. In other embodiments, the Surgical Computer 150 may be aparallel computing platform that uses multiple central processing units(CPUs) or graphics processing units (GPU) to perform processing. In someembodiments, the Surgical Computer 150 is connected to a remote serverover one or more computer networks (e.g., the Internet). The remoteserver can be used, for example, for storage of data or execution ofcomputationally intensive processing tasks.

Various techniques generally known in the art can be used for connectingthe Surgical Computer 150 to the other components of the CASS 100.Moreover, the computers can connect to the Surgical Computer 150 using amix of technologies. For example, the End Effector 105B may connect tothe Surgical Computer 150 over a wired (i.e., serial) connection. TheTracking System 115, Tissue Navigation System 120, and Display 125 cansimilarly be connected to the Surgical Computer 150 using wiredconnections. Alternatively, the Tracking System 115, Tissue NavigationSystem 120, and Display 125 may connect to the Surgical Computer 150using wireless technologies such as, without limitation, Wi-Fi,Bluetooth, Near Field Communication (NFC), or ZigBee.

Powered Impaction and Acetabular Reamer Devices

Part of the flexibility of the CASS design described above with respectto FIG. 1 is that additional or alternative devices can be added to theCASS 100 as necessary to support particular surgical procedures. Forexample, in the context of hip surgeries, the CASS 100 may include apowered impaction device. Impaction devices are designed to repeatedlyapply an impaction force that the surgeon can use to perform activitiessuch as implant alignment. For example, within a total hip arthroplasty(THA), a surgeon will often insert a prosthetic acetabular cup into theimplant host's acetabulum using an impaction device. Although impactiondevices can be manual in nature (e.g., operated by the surgeon strikingan impactor with a mallet), powered impaction devices are generallyeasier and quicker to use in the surgical setting. Powered impactiondevices may be powered, for example, using a battery attached to thedevice. Various attachment pieces may be connected to the poweredimpaction device to allow the impaction force to be directed in variousways as needed during surgery. Also, in the context of hip surgeries,the CASS 100 may include a powered, robotically controlled end effectorto ream the acetabulum to accommodate an acetabular cup implant.

In a robotically-assisted THA, the patient's anatomy can be registeredto the CASS 100 using CT or other image data, the identification ofanatomical landmarks, tracker arrays attached to the patient's bones,and one or more cameras. Tracker arrays can be mounted on the iliaccrest using clamps and/or bone pins and such trackers can be mountedexternally through the skin or internally (either posterolaterally oranterolaterally) through the incision made to perform the THA. For aTHA, the CASS 100 can utilize one or more femoral cortical screwsinserted into the proximal femur as checkpoints to aid in theregistration process. The CASS 100 also can utilize one or morecheckpoint screws inserted into the pelvis as additional checkpoints toaid in the registration process. Femoral tracker arrays can be securedto or mounted in the femoral cortical screws. The CASS 100 can employsteps where the registration is verified using a probe that the surgeonprecisely places on key areas of the proximal femur and pelvisidentified for the surgeon on the display 125. Trackers can be locatedon the robotic arm 105A or end effector 105B to register the arm and/orend effector to the CASS 100. The verification step also can utilizeproximal and distal femoral checkpoints. The CASS 100 can utilize colorprompts or other prompts to inform the surgeon that the registrationprocess for the relevant bones and the robotic arm 105A or end effector105B has been verified to a certain degree of accuracy (e.g., within 1mm).

For a THA, the CASS 100 can include a broach tracking option usingfemoral arrays to allow the surgeon to intraoperatively capture thebroach position and orientation and calculate hip length and offsetvalues for the patient. Based on information provided about thepatient's hip joint and the planned implant position and orientationafter broach tracking is completed, the surgeon can make modificationsor adjustments to the surgical plan.

For a robotically-assisted THA, the CASS 100 can include one or morepowered reamers connected or attached to a robotic arm 105A or endeffector 105B that prepares the pelvic bone to receive an acetabularimplant according to a surgical plan. The robotic arm 105A and/or endeffector 105B can inform the surgeon and/or control the power of thereamer to ensure that the acetabulum is being resected (reamed) inaccordance with the surgical plan. For example, if the surgeon attemptsto resect bone outside of the boundary of the bone to be resected inaccordance with the surgical plan, the CASS 100 can power off the reameror instruct the surgeon to power off the reamer. The CASS 100 canprovide the surgeon with an option to turn off or disengage the roboticcontrol of the reamer. The display 125 can depict the progress of thebone being resected (reamed) as compared to the surgical plan usingdifferent colors. The surgeon can view the display of the bone beingresected (reamed) to guide the reamer to complete the reaming inaccordance with the surgical plan. The CASS 100 can provide visual oraudible prompts to the surgeon to warn the surgeon that resections arebeing made that are not in accordance with the surgical plan.

Following reaming, the CASS 100 can employ a manual or powered impactorthat is attached or connected to the robotic arm 105A or end effector105B to impact trial implants and final implants into the acetabulum.The robotic arm 105A and/or end effector 105B can be used to guide theimpactor to impact the trial and final implants into the acetabulum inaccordance with the surgical plan. The CASS 100 can cause the positionand orientation of the trial and final implants vis-à-vis the bone to bedisplayed to inform the surgeon as to how the trial and final implant'sorientation and position compare to the surgical plan, and the display125 can show the implant's position and orientation as the surgeonmanipulates the leg and hip. The CASS 100 can provide the surgeon withthe option of re-planning and re-doing the reaming and implant impactionby preparing a new surgical plan if the surgeon is not satisfied withthe original implant position and orientation.

Preoperatively, the CASS 100 can develop a proposed surgical plan basedon a three dimensional model of the hip joint and other informationspecific to the patient, such as the mechanical and anatomical axes ofthe leg bones, the epicondylar axis, the femoral neck axis, thedimensions (e.g., length) of the femur and hip, the midline axis of thehip joint, the ASIS axis of the hip joint, and the location ofanatomical landmarks such as the lesser trochanter landmarks, the distallandmark, and the center of rotation of the hip joint. TheCASS-developed surgical plan can provide a recommended optimal implantsize and implant position and orientation based on the three dimensionalmodel of the hip joint and other information specific to the patient.The CASS-developed surgical plan can include proposed details on offsetvalues, inclination and anteversion values, center of rotation, cupsize, medialization values, superior-inferior fit values, femoral stemsizing and length.

For a THA, the CASS-developed surgical plan can be viewed preoperativelyand intraoperatively, and the surgeon can modify CASS-developed surgicalplan preoperatively or intraoperatively. The CASS-developed surgicalplan can display the planned resection to the hip joint and superimposethe planned implants onto the hip joint based on the planned resections.The CASS 100 can provide the surgeon with options for different surgicalworkflows that will be displayed to the surgeon based on a surgeon'spreference. For example, the surgeon can choose from different workflowsbased on the number and types of anatomical landmarks that are checkedand captured and/or the location and number of tracker arrays used inthe registration process.

According to some embodiments, a powered impaction device used with theCASS 100 may operate with a variety of different settings. In someembodiments, the surgeon adjusts settings through a manual switch orother physical mechanism on the powered impaction device. In otherembodiments, a digital interface may be used that allows setting entry,for example, via a touchscreen on the powered impaction device. Such adigital interface may allow the available settings to vary based, forexample, on the type of attachment piece connected to the powerattachment device. In some embodiments, rather than adjusting thesettings on the powered impaction device itself, the settings can bechanged through communication with a robot or other computer systemwithin the CASS 100. Such connections may be established using, forexample, a Bluetooth or Wi-Fi networking module on the powered impactiondevice. In another embodiment, the impaction device and end pieces maycontain features that allow the impaction device to be aware of what endpiece (cup impactor, broach handle, etc.) is attached with no actionrequired by the surgeon, and adjust the settings accordingly. This maybe achieved, for example, through a QR code, barcode, RFID tag, or othermethod.

Examples of the settings that may be used include cup impaction settings(e.g., single direction, specified frequency range, specified forceand/or energy range); broach impaction settings (e.g., dualdirection/oscillating at a specified frequency range, specified forceand/or energy range); femoral head impaction settings (e.g., singledirection/single blow at a specified force or energy); and stemimpaction settings (e.g., single direction at specified frequency with aspecified force or energy). Additionally, in some embodiments, thepowered impaction device includes settings related to acetabular linerimpaction (e.g., single direction/single blow at a specified force orenergy). There may be a plurality of settings for each type of linersuch as poly, ceramic, oxinium, or other materials. Furthermore, thepowered impaction device may offer settings for different bone qualitybased on preoperative testing/imaging/knowledge and/or intraoperativeassessment by surgeon. In some embodiments, the powered impactor devicemay have a dual function. For example, the powered impactor device notonly could provide reciprocating motion to provide an impact force, butalso could provide reciprocating motion for a broach or rasp.

In some embodiments, the powered impaction device includes feedbacksensors that gather data during instrument use and send data to acomputing device, such as a controller within the device or the SurgicalComputer 150. This computing device can then record the data for lateranalysis and use. Examples of the data that may be collected include,without limitation, sound waves, the predetermined resonance frequencyof each instrument, reaction force or rebound energy from patient bone,location of the device with respect to imaging (e.g., fluoro, CT,ultrasound, MRI, etc.) registered bony anatomy, and/or external straingauges on bones.

Once the data is collected, the computing device may execute one or morealgorithms in real-time or near real-time to aid the surgeon inperforming the surgical procedure. For example, in some embodiments, thecomputing device uses the collected data to derive information such asthe proper final broach size (femur); when the stem is fully seated(femur side); or when the cup is seated (depth and/or orientation) for aTHA. Once the information is known, it may be displayed for thesurgeon's review, or it may be used to activate haptics or otherfeedback mechanisms to guide the surgical procedure.

Additionally, the data derived from the aforementioned algorithms may beused to drive operation of the device. For example, during insertion ofa prosthetic acetabular cup with a powered impaction device, the devicemay automatically extend an impaction head (e.g., an end effector)moving the implant into the proper location, or turn the power off tothe device once the implant is fully seated. In one embodiment, thederived information may be used to automatically adjust settings forquality of bone where the powered impaction device should use less powerto mitigate femoral/acetabular/pelvic fracture or damage to surroundingtissues.

Robotic Arm

In some embodiments, the CASS 100 includes a robotic arm 105A thatserves as an interface to stabilize and hold a variety of instrumentsused during the surgical procedure. For example, in the context of a hipsurgery, these instruments may include, without limitation, retractors,a sagittal or reciprocating saw, the reamer handle, the cup impactor,the broach handle, and the stem inserter. The robotic arm 105A may havemultiple degrees of freedom (like a Spider device), and have the abilityto be locked in place (e.g., by a press of a button, voice activation, asurgeon removing a hand from the robotic arm, or other method).

In some embodiments, movement of the robotic arm 105A may be effectuatedby use of a control panel built into the robotic arm system. Forexample, a display screen may include one or more input sources, such asphysical buttons or a user interface having one or more icons, thatdirect movement of the robotic arm 105A. The surgeon or other healthcareprofessional may engage with the one or more input sources to positionthe robotic arm 105A when performing a surgical procedure.

A tool or an end effector 105B attached or integrated into a robotic arm105A may include, without limitation, a burring device, a scalpel, acutting device, a retractor, a joint tensioning device, or the like. Inembodiments in which an end effector 105B is used, the end effector maybe positioned at the end of the robotic arm 105A such that any motorcontrol operations are performed within the robotic arm system. Inembodiments in which a tool is used, the tool may be secured at a distalend of the robotic arm 105A, but motor control operation may residewithin the tool itself.

The robotic arm 105A may be motorized internally to both stabilize therobotic arm, thereby preventing it from falling and hitting the patient,surgical table, surgical staff, etc., and to allow the surgeon to movethe robotic arm without having to fully support its weight. While thesurgeon is moving the robotic arm 105A, the robotic arm may provide someresistance to prevent the robotic arm from moving too fast or having toomany degrees of freedom active at once. The position and the lock statusof the robotic arm 105A may be tracked, for example, by a controller orthe Surgical Computer 150.

In some embodiments, the robotic arm 105A can be moved by hand (e.g., bythe surgeon) or with internal motors into its ideal position andorientation for the task being performed. In some embodiments, therobotic arm 105A may be enabled to operate in a “free” mode that allowsthe surgeon to position the arm into a desired position without beingrestricted. While in the free mode, the position and orientation of therobotic arm 105A may still be tracked as described above. In oneembodiment, certain degrees of freedom can be selectively released uponinput from user (e.g., surgeon) during specified portions of thesurgical plan tracked by the Surgical Computer 150. Designs in which arobotic arm 105A is internally powered through hydraulics or motors orprovides resistance to external manual motion through similar means canbe described as powered robotic arms, while arms that are manuallymanipulated without power feedback, but which may be manually orautomatically locked in place, may be described as passive robotic arms.

A robotic arm 105A or end effector 105B can include a trigger or othermeans to control the power of a saw or drill. Engagement of the triggeror other means by the surgeon can cause the robotic arm 105A or endeffector 105B to transition from a motorized alignment mode to a modewhere the saw or drill is engaged and powered on. Additionally, the CASS100 can include a foot pedal (not shown) that causes the system toperform certain functions when activated. For example, the surgeon canactivate the foot pedal to instruct the CASS 100 to place the roboticarm 105A or end effector 105B in an automatic mode that brings therobotic arm or end effector into the proper position with respect to thepatient's anatomy in order to perform the necessary resections. The CASS100 also can place the robotic arm 105A or end effector 105B in acollaborative mode that allows the surgeon to manually manipulate andposition the robotic arm or end effector into a particular location. Thecollaborative mode can be configured to allow the surgeon to move therobotic arm 105A or end effector 105B medially or laterally, whilerestricting movement in other directions. As discussed, the robotic arm105A or end effector 105B can include a cutting device (saw, drill, andburr) or a cutting guide or jig 105D that will guide a cutting device.In other embodiments, movement of the robotic arm 105A or roboticallycontrolled end effector 105B can be controlled entirely by the CASS 100without any, or with only minimal, assistance or input from a surgeon orother medical professional. In still other embodiments, the movement ofthe robotic arm 105A or robotically controlled end effector 105B can becontrolled remotely by a surgeon or other medical professional using acontrol mechanism separate from the robotic arm or roboticallycontrolled end effector device, for example using a joystick orinteractive monitor or display control device.

The examples below describe uses of the robotic device in the context ofa hip surgery; however, it should be understood that the robotic arm mayhave other applications for surgical procedures involving knees,shoulders, etc. One example of use of a robotic arm in the context offorming an anterior cruciate ligament (ACL) graft tunnel is described inWIPO Publication No. WO 2020/047051, filed Aug. 28, 2019, entitled“Robotic Assisted Ligament Graft Placement and Tensioning,” the entiretyof which is incorporated herein by reference.

A robotic arm 105A may be used for holding the retractor. For example inone embodiment, the robotic arm 105A may be moved into the desiredposition by the surgeon. At that point, the robotic arm 105A may lockinto place. In some embodiments, the robotic arm 105A is provided withdata regarding the patient's position, such that if the patient moves,the robotic arm can adjust the retractor position accordingly. In someembodiments, multiple robotic arms may be used, thereby allowingmultiple retractors to be held or for more than one activity to beperformed simultaneously (e.g., retractor holding & reaming).

The robotic arm 105A may also be used to help stabilize the surgeon'shand while making a femoral neck cut. In this application, control ofthe robotic arm 105A may impose certain restrictions to prevent softtissue damage from occurring. For example, in one embodiment, theSurgical Computer 150 tracks the position of the robotic arm 105A as itoperates. If the tracked location approaches an area where tissue damageis predicted, a command may be sent to the robotic arm 105A causing itto stop. Alternatively, where the robotic arm 105A is automaticallycontrolled by the Surgical Computer 150, the Surgical Computer mayensure that the robotic arm is not provided with any instructions thatcause it to enter areas where soft tissue damage is likely to occur. TheSurgical Computer 150 may impose certain restrictions on the surgeon toprevent the surgeon from reaming too far into the medial wall of theacetabulum or reaming at an incorrect angle or orientation.

In some embodiments, the robotic arm 105A may be used to hold a cupimpactor at a desired angle or orientation during cup impaction. Whenthe final position has been achieved, the robotic arm 105A may preventany further seating to prevent damage to the pelvis.

The surgeon may use the robotic arm 105A to position the broach handleat the desired position and allow the surgeon to impact the broach intothe femoral canal at the desired orientation. In some embodiments, oncethe Surgical Computer 150 receives feedback that the broach is fullyseated, the robotic arm 105A may restrict the handle to prevent furtheradvancement of the broach.

The robotic arm 105A may also be used for resurfacing applications. Forexample, the robotic arm 105A may stabilize the surgeon while usingtraditional instrumentation and provide certain restrictions orlimitations to allow for proper placement of implant components (e.g.,guide wire placement, chamfer cutter, sleeve cutter, plan cutter, etc.).Where only a burr is employed, the robotic arm 105A may stabilize thesurgeon's handpiece and may impose restrictions on the handpiece toprevent the surgeon from removing unintended bone in contravention ofthe surgical plan.

The robotic arm 105A may be a passive arm. As an example, the roboticarm 105A may be a CIRQ robot arm available from Brainlab AG. CIRQ is aregistered trademark of Brainlab AG, Olof-Palme-Str. 9 81829, München,FED REP of GERMANY. In one particular embodiment, the robotic arm 105Ais an intelligent holding arm as disclosed in U.S. patent applicationSer. No. 15/525,585 to Krinninger et al., U.S. patent application Ser.No. 15/561,042 to Nowatschin et al., U.S. patent application Ser. No.15/561,048 to Nowatschin et al., and U.S. Pat. No. 10,342,636 toNowatschin et al., the entire contents of each of which is hereinincorporated by reference.

Surgical Procedure Data Generation and Collection

The various services that are provided by medical professionals to treata clinical condition are collectively referred to as an “episode ofcare.” For a particular surgical intervention the episode of care caninclude three phases: pre-operative, intra-operative, andpost-operative. During each phase, data is collected or generated thatcan be used to analyze the episode of care in order to understandvarious features of the procedure and identify patterns that may beused, for example, in training models to make decisions with minimalhuman intervention. The data collected over the episode of care may bestored at the Surgical Computer 150 or the Surgical Data Server 180 as acomplete dataset. Thus, for each episode of care, a dataset exists thatcomprises all of the data collectively pre-operatively about thepatient, all of the data collected or stored by the CASS 100intra-operatively, and any post-operative data provided by the patientor by a healthcare professional monitoring the patient.

As explained in further detail, the data collected during the episode ofcare may be used to enhance performance of the surgical procedure or toprovide a holistic understanding of the surgical procedure and thepatient outcomes. For example, in some embodiments, the data collectedover the episode of care may be used to generate a surgical plan. In oneembodiment, a high-level, pre-operative plan is refinedintra-operatively as data is collected during surgery. In this way, thesurgical plan can be viewed as dynamically changing in real-time or nearreal-time as new data is collected by the components of the CASS 100. Inother embodiments, pre-operative images or other input data may be usedto develop a robust plan preoperatively that is simply executed duringsurgery. In this case, the data collected by the CASS 100 during surgerymay be used to make recommendations that ensure that the surgeon stayswithin the pre-operative surgical plan. For example, if the surgeon isunsure how to achieve a certain prescribed cut or implant alignment, theSurgical Computer 150 can be queried for a recommendation. In stillother embodiments, the pre-operative and intra-operative planningapproaches can be combined such that a robust pre-operative plan can bedynamically modified, as necessary or desired, during the surgicalprocedure. In some embodiments, a biomechanics-based model of patientanatomy contributes simulation data to be considered by the CASS 100 indeveloping preoperative, intraoperative, andpost-operative/rehabilitation procedures to optimize implant performanceoutcomes for the patient.

Aside from changing the surgical procedure itself, the data gatheredduring the episode of care may be used as an input to other proceduresancillary to the surgery. For example, in some embodiments, implants canbe designed using episode of care data. Example data-driven techniquesfor designing, sizing, and fitting implants are described in U.S. patentapplication Ser. No. 13/814,531 filed Aug. 15, 2011 and entitled“Systems and Methods for Optimizing Parameters for OrthopaedicProcedures”; U.S. patent application Ser. No. 14/232,958 filed Jul. 20,2012 and entitled “Systems and Methods for Optimizing Fit of an Implantto Anatomy”; and U.S. patent application Ser. No. 12/234,444 filed Sep.19, 2008 and entitled “Operatively Tuning Implants for IncreasedPerformance,” the entire contents of each of which are herebyincorporated by reference into this patent application.

Furthermore, the data can be used for educational, training, or researchpurposes. For example, using the network-based approach described belowin FIG. 5C, other doctors or students can remotely view surgeries ininterfaces that allow them to selectively view data as it is collectedfrom the various components of the CASS 100. After the surgicalprocedure, similar interfaces may be used to “playback” a surgery fortraining or other educational purposes, or to identify the source of anyissues or complications with the procedure.

Data acquired during the pre-operative phase generally includes allinformation collected or generated prior to the surgery. Thus, forexample, information about the patient may be acquired from a patientintake form or electronic medical record (EMR). Examples of patientinformation that may be collected include, without limitation, patientdemographics, diagnoses, medical histories, progress notes, vital signs,medical history information, allergies, and lab results. Thepre-operative data may also include images related to the anatomicalarea of interest. These images may be captured, for example, usingMagnetic Resonance Imaging (MRI), Computed Tomography (CT), X-ray,ultrasound, or any other modality known in the art. The pre-operativedata may also comprise quality of life data captured from the patient.For example, in one embodiment, pre-surgery patients use a mobileapplication (“app”) to answer questionnaires regarding their currentquality of life. In some embodiments, preoperative data used by the CASS100 includes demographic, anthropometric, cultural, or other specifictraits about a patient that can coincide with activity levels andspecific patient activities to customize the surgical plan to thepatient. For example, certain cultures or demographics may be morelikely to use a toilet that requires squatting on a daily basis.

FIGS. 5A and 5B provide examples of data that may be acquired during theintra-operative phase of an episode of care. These examples are based onthe various components of the CASS 100 described above with reference toFIG. 1 ; however, it should be understood that other types of data maybe used based on the types of equipment used during surgery and theiruse.

FIG. 5A shows examples of some of the control instructions that theSurgical Computer 150 provides to other components of the CASS 100,according to some embodiments. Note that the example of FIG. 5A assumesthat the components of the Effector Platform 105 are each controlleddirectly by the Surgical Computer 150. In embodiments where a componentis manually controlled by the Surgeon 111, instructions may be providedon the Display 125 or AR HMD 155 instructing the Surgeon 111 how to movethe component.

The various components included in the Effector Platform 105 arecontrolled by the Surgical Computer 150 providing position commands thatinstruct the component where to move within a coordinate system. In someembodiments, the Surgical Computer 150 provides the Effector Platform105 with instructions defining how to react when a component of theEffector Platform 105 deviates from a surgical plan. These commands arereferenced in FIG. 5A as “haptic” commands. For example, the EndEffector 105B may provide a force to resist movement outside of an areawhere resection is planned. Other commands that may be used by theEffector Platform 105 include vibration and audio cues.

In some embodiments, the end effectors 105B of the robotic arm 105A areoperatively coupled with cutting guide 105D. In response to ananatomical model of the surgical scene, the robotic arm 105A can movethe end effectors 105B and the cutting guide 105D into position to matchthe location of the femoral or tibial cut to be performed in accordancewith the surgical plan. This can reduce the likelihood of error,allowing the vision system and a processor utilizing that vision systemto implement the surgical plan to place a cutting guide 105D at theprecise location and orientation relative to the tibia or femur to aligna cutting slot of the cutting guide with the cut to be performedaccording to the surgical plan. Then, a surgeon can use any suitabletool, such as an oscillating or rotating saw or drill to perform the cut(or drill a hole) with perfect placement and orientation because thetool is mechanically limited by the features of the cutting guide 105D.In some embodiments, the cutting guide 105D may include one or more pinholes that are used by a surgeon to drill and screw or pin the cuttingguide into place before performing a resection of the patient tissueusing the cutting guide. This can free the robotic arm 105A or ensurethat the cutting guide 105D is fully affixed without moving relative tothe bone to be resected. For example, this procedure can be used to makethe first distal cut of the femur during a total knee arthroplasty. Insome embodiments, where the arthroplasty is a hip arthroplasty, cuttingguide 105D can be fixed to the femoral head or the acetabulum for therespective hip arthroplasty resection. It should be understood that anyarthroplasty that utilizes precise cuts can use the robotic arm 105Aand/or cutting guide 105D in this manner.

The Resection Equipment 110 is provided with a variety of commands toperform bone or tissue operations. As with the Effector Platform 105,position information may be provided to the Resection Equipment 110 tospecify where it should be located when performing resection. Othercommands provided to the Resection Equipment 110 may be dependent on thetype of resection equipment. For example, for a mechanical or ultrasonicresection tool, the commands may specify the speed and frequency of thetool. For Radiofrequency Ablation (RFA) and other laser ablation tools,the commands may specify intensity and pulse duration.

Some components of the CASS 100 do not need to be directly controlled bythe Surgical Computer 150; rather, the Surgical Computer 150 only needsto activate the component, which then executes software locallyspecifying the manner in which to collect data and provide it to theSurgical Computer 150. In the example of FIG. 5A, there are twocomponents that are operated in this manner: the Tracking System 115 andthe Tissue Navigation System 120.

The Surgical Computer 150 provides the Display 125 with anyvisualization that is needed by the Surgeon 111 during surgery. Formonitors, the Surgical Computer 150 may provide instructions fordisplaying images, GUIs, etc. using techniques known in the art. Thedisplay 125 can include various portions of the workflow of a surgicalplan. During the registration process, for example, the display 125 canshow a preoperatively constructed 3D bone model and depict the locationsof the probe as the surgeon uses the probe to collect locations ofanatomical landmarks on the patient. The display 125 can includeinformation about the surgical target area. For example, in connectionwith a TKA, the display 125 can depict the mechanical and anatomicalaxes of the femur and tibia. The display 125 can depict varus and valgusangles for the knee joint based on a surgical plan, and the CASS 100 candepict how such angles will be affected if contemplated revisions to thesurgical plan are made. Accordingly, the display 125 is an interactiveinterface that can dynamically update and display how changes to thesurgical plan would impact the procedure and the final position andorientation of implants installed on bone.

As the workflow progresses to preparation of bone cuts or resections,the display 125 can depict the planned or recommended bone cuts beforeany cuts are performed. The surgeon 111 can manipulate the image displayto provide different anatomical perspectives of the target area and canhave the option to alter or revise the planned bone cuts based onintraoperative evaluation of the patient. The display 125 can depict howthe chosen implants would be installed on the bone if the planned bonecuts are performed. If the surgeon 111 choses to change the previouslyplanned bone cuts, the display 125 can depict how the revised bone cutswould change the position and orientation of the implant when installedon the bone.

The display 125 can provide the surgeon 111 with a variety of data andinformation about the patient, the planned surgical intervention, andthe implants. Various patient-specific information can be displayed,including real-time data concerning the patient's health such as heartrate, blood pressure, etc. The display 125 also can include informationabout the anatomy of the surgical target region including the locationof landmarks, the current state of the anatomy (e.g., whether anyresections have been made, the depth and angles of planned and executedbone cuts), and future states of the anatomy as the surgical planprogresses. The display 125 also can provide or depict additionalinformation about the surgical target region. For a TKA, the display 125can provide information about the gaps (e.g., gap balancing) between thefemur and tibia and how such gaps will change if the planned surgicalplan is carried out. For a TKA, the display 125 can provide additionalrelevant information about the knee joint such as data about the joint'stension (e.g., ligament laxity) and information concerning rotation andalignment of the joint. The display 125 can depict how the plannedimplants' locations and positions will affect the patient as the kneejoint is flexed. The display 125 can depict how the use of differentimplants or the use of different sizes of the same implant will affectthe surgical plan and preview how such implants will be positioned onthe bone. The CASS 100 can provide such information for each of theplanned bone resections in a TKA or THA. In a TKA, the CASS 100 canprovide robotic control for one or more of the planned bone resections.For example, the CASS 100 can provide robotic control only for theinitial distal femur cut, and the surgeon 111 can manually perform otherresections (anterior, posterior and chamfer cuts) using conventionalmeans, such as a 4-in-1 cutting guide or jig 105D.

The display 125 can employ different colors to inform the surgeon of thestatus of the surgical plan. For example, un-resected bone can bedisplayed in a first color, resected bone can be displayed in a secondcolor, and planned resections can be displayed in a third color.Implants can be superimposed onto the bone in the display 125, andimplant colors can change or correspond to different types or sizes ofimplants.

The information and options depicted on the display 125 can varydepending on the type of surgical procedure being performed. Further,the surgeon 111 can request or select a particular surgical workflowdisplay that matches or is consistent with his or her surgical planpreferences. For example, for a surgeon 111 who typically performs thetibial cuts before the femoral cuts in a TKA, the display 125 andassociated workflow can be adapted to take this preference into account.The surgeon 111 also can preselect that certain steps be included ordeleted from the standard surgical workflow display. For example, if asurgeon 111 uses resection measurements to finalize an implant plan butdoes not analyze ligament gap balancing when finalizing the implantplan, the surgical workflow display can be organized into modules, andthe surgeon can select which modules to display and the order in whichthe modules are provided based on the surgeon's preferences or thecircumstances of a particular surgery. Modules directed to ligament andgap balancing, for example, can include pre- and post-resectionligament/gap balancing, and the surgeon 111 can select which modules toinclude in their default surgical plan workflow depending on whetherthey perform such ligament and gap balancing before or after (or both)bone resections are performed.

For more specialized display equipment, such as AR HMDs, the SurgicalComputer 150 may provide images, text, etc. using the data formatsupported by the equipment. For example, if the Display 125 is aholography device such as the Microsoft HoloLens™ or Magic Leap One™,the Surgical Computer 150 may use the HoloLens Application ProgramInterface (API) to send commands specifying the position and content ofholograms displayed in the field of view of the Surgeon 111.

In some embodiments, one or more surgical planning models may beincorporated into the CASS 100 and used in the development of thesurgical plans provided to the surgeon 111. The term “surgical planningmodel” refers to software that simulates the biomechanics performance ofanatomy under various scenarios to determine the optimal way to performcutting and other surgical activities. For example, for knee replacementsurgeries, the surgical planning model can measure parameters forfunctional activities, such as deep knee bends, gait, etc., and selectcut locations on the knee to optimize implant placement. One example ofa surgical planning model is the LIFEMOD™ simulation software from SMITHAND NEPHEW, INC. In some embodiments, the Surgical Computer 150 includescomputing architecture that allows full execution of the surgicalplanning model during surgery (e.g., a GPU-based parallel processingenvironment). In other embodiments, the Surgical Computer 150 may beconnected over a network to a remote computer that allows suchexecution, such as a Surgical Data Server 180 (see FIG. 5C). As analternative to full execution of the surgical planning model, in someembodiments, a set of transfer functions are derived that simplify themathematical operations captured by the model into one or more predictorequations. Then, rather than execute the full simulation during surgery,the predictor equations are used. Further details on the use of transferfunctions are described in WIPO Publication No. 2020/037308, filed Aug.19, 2019, entitled “Patient Specific Surgical Method and System,” theentirety of which is incorporated herein by reference.

FIG. 5B shows examples of some of the types of data that can be providedto the Surgical Computer 150 from the various components of the CASS100. In some embodiments, the components may stream data to the SurgicalComputer 150 in real-time or near real-time during surgery. In otherembodiments, the components may queue data and send it to the SurgicalComputer 150 at set intervals (e.g., every second). Data may becommunicated using any format known in the art. Thus, in someembodiments, the components all transmit data to the Surgical Computer150 in a common format. In other embodiments, each component may use adifferent data format, and the Surgical Computer 150 is configured withone or more software applications that enable translation of the data.

In general, the Surgical Computer 150 may serve as the central pointwhere CASS data is collected. The exact content of the data will varydepending on the source. For example, each component of the EffectorPlatform 105 provides a measured position to the Surgical Computer 150.Thus, by comparing the measured position to a position originallyspecified by the Surgical Computer 150 (see FIG. 5B), the SurgicalComputer can identify deviations that take place during surgery.

The Resection Equipment 110 can send various types of data to theSurgical Computer 150 depending on the type of equipment used. Exampledata types that may be sent include the measured torque, audiosignatures, and measured displacement values. Similarly, the TrackingTechnology 115 can provide different types of data depending on thetracking methodology employed. Example tracking data types includeposition values for tracked items (e.g., anatomy, tools, etc.),ultrasound images, and surface or landmark collection points or axes.The Tissue Navigation System 120 provides the Surgical Computer 150 withanatomic locations, shapes, etc. as the system operates.

Although the Display 125 generally is used for outputting data forpresentation to the user, it may also provide data to the SurgicalComputer 150. For example, for embodiments where a monitor is used aspart of the Display 125, the Surgeon 111 may interact with a GUI toprovide inputs which are sent to the Surgical Computer 150 for furtherprocessing. For AR applications, the measured position and displacementof the HMD may be sent to the Surgical Computer 150 so that it canupdate the presented view as needed.

During the post-operative phase of the episode of care, various types ofdata can be collected to quantify the overall improvement ordeterioration in the patient's condition as a result of the surgery. Thedata can take the form of, for example, self-reported informationreported by patients via questionnaires. For example, in the context ofa knee replacement surgery, functional status can be measured with anOxford Knee Score questionnaire, and the post-operative quality of lifecan be measured with a EQ5D-5L questionnaire. Other examples in thecontext of a hip replacement surgery may include the Oxford Hip Score,Harris Hip Score, and WOMAC (Western Ontario and McMaster UniversitiesOsteoarthritis index). Such questionnaires can be administered, forexample, by a healthcare professional directly in a clinical setting orusing a mobile app that allows the patient to respond to questionsdirectly. In some embodiments, the patient may be outfitted with one ormore wearable devices that collect data relevant to the surgery. Forexample, following a knee surgery, the patient may be outfitted with aknee brace that includes sensors that monitor knee positioning,flexibility, etc. This information can be collected and transferred tothe patient's mobile device for review by the surgeon to evaluate theoutcome of the surgery and address any issues. In some embodiments, oneor more cameras can capture and record the motion of a patient's bodysegments during specified activities postoperatively. This motioncapture can be compared to a biomechanics model to better understand thefunctionality of the patient's joints and better predict progress inrecovery and identify any possible revisions that may be needed.

The post-operative stage of the episode of care can continue over theentire life of a patient. For example, in some embodiments, the SurgicalComputer 150 or other components comprising the CASS 100 can continue toreceive and collect data relevant to a surgical procedure after theprocedure has been performed. This data may include, for example,images, answers to questions, “normal” patient data (e.g., blood type,blood pressure, conditions, medications, etc.), biometric data (e.g.,gait, etc.), and objective and subjective data about specific issues(e.g., knee or hip joint pain). This data may be explicitly provided tothe Surgical Computer 150 or other CASS component by the patient or thepatient's physician(s). Alternatively or additionally, the SurgicalComputer 150 or other CASS component can monitor the patient's EMR andretrieve relevant information as it becomes available. This longitudinalview of the patient's recovery allows the Surgical Computer 150 or otherCASS component to provide a more objective analysis of the patient'soutcome to measure and track success or lack of success for a givenprocedure. For example, a condition experienced by a patient long afterthe surgical procedure can be linked back to the surgery through aregression analysis of various data items collected during the episodeof care. This analysis can be further enhanced by performing theanalysis on groups of patients that had similar procedures and/or havesimilar anatomies.

In some embodiments, data is collected at a central location to providefor easier analysis and use. Data can be manually collected from variousCASS components in some instances. For example, a portable storagedevice (e.g., USB stick) can be attached to the Surgical Computer 150into order to retrieve data collected during surgery. The data can thenbe transferred, for example, via a desktop computer to the centralizedstorage. Alternatively, in some embodiments, the Surgical Computer 150is connected directly to the centralized storage via a Network 175 asshown in FIG. 5C.

FIG. 5C illustrates a “cloud-based” implementation in which the SurgicalComputer 150 is connected to a Surgical Data Server 180 via a Network175. This Network 175 may be, for example, a private intranet or theInternet. In addition to the data from the Surgical Computer 150, othersources can transfer relevant data to the Surgical Data Server 180. Theexample of FIG. 5C shows 3 additional data sources: the Patient 160,Healthcare Professional(s) 165, and an EMR Database 170. Thus, thePatient 160 can send pre-operative and post-operative data to theSurgical Data Server 180, for example, using a mobile app. TheHealthcare Professional(s) 165 includes the surgeon and his or her staffas well as any other professionals working with Patient 160 (e.g., apersonal physician, a rehabilitation specialist, etc.). It should alsobe noted that the EMR Database 170 may be used for both pre-operativeand post-operative data. For example, assuming that the Patient 160 hasgiven adequate permissions, the Surgical Data Server 180 may collect theEMR of the Patient pre-surgery. Then, the Surgical Data Server 180 maycontinue to monitor the EMR for any updates post-surgery.

At the Surgical Data Server 180, an Episode of Care Database 185 is usedto store the various data collected over a patient's episode of care.The Episode of Care Database 185 may be implemented using any techniqueknown in the art. For example, in some embodiments, a SQL-based databasemay be used where all of the various data items are structured in amanner that allows them to be readily incorporated in two SQL'scollection of rows and columns. However, in other embodiments a No-SQLdatabase may be employed to allow for unstructured data, while providingthe ability to rapidly process and respond to queries. As is understoodin the art, the term “No-SQL” is used to define a class of data storesthat are non-relational in their design. Various types of No-SQLdatabases may generally be grouped according to their underlying datamodel. These groupings may include databases that use column-based datamodels (e.g., Cassandra), document-based data models (e.g., MongoDB),key-value based data models (e.g., Redis), and/or graph-based datamodels (e.g., Allego). Any type of No-SQL database may be used toimplement the various embodiments described herein and, in someembodiments, the different types of databases may support the Episode ofCare Database 185.

Data can be transferred between the various data sources and theSurgical Data Server 180 using any data format and transfer techniqueknown in the art. It should be noted that the architecture shown in FIG.5C allows transmission from the data source to the Surgical Data Server180, as well as retrieval of data from the Surgical Data Server 180 bythe data sources. For example, as explained in detail below, in someembodiments, the Surgical Computer 150 may use data from past surgeries,machine learning models, etc. to help guide the surgical procedure.

In some embodiments, the Surgical Computer 150 or the Surgical DataServer 180 may execute a de-identification process to ensure that datastored in the Episode of Care Database 185 meets Health InsurancePortability and Accountability Act (HIPAA) standards or otherrequirements mandated by law. HIPAA provides a list of certainidentifiers that must be removed from data during de-identification. Theaforementioned de-identification process can scan for these identifiersin data that is transferred to the Episode of Care Database 185 forstorage. For example, in one embodiment, the Surgical Computer 150executes the de-identification process just prior to initiating transferof a particular data item or set of data items to the Surgical DataServer 180. In some embodiments, a unique identifier is assigned to datafrom a particular episode of care to allow for re-identification of thedata if necessary.

Although FIGS. 5A-5C discuss data collection in the context of a singleepisode of care, it should be understood that the general concept can beextended to data collection from multiple episodes of care. For example,surgical data may be collected over an entire episode of care each timea surgery is performed with the CASS 100 and stored at the SurgicalComputer 150 or at the Surgical Data Server 180. As explained in furtherdetail below, a robust database of episode of care data allows thegeneration of optimized values, measurements, distances, or otherparameters and other recommendations related to the surgical procedure.In some embodiments, the various datasets are indexed in the database orother storage medium in a manner that allows for rapid retrieval ofrelevant information during the surgical procedure. For example, in oneembodiment, a patient-centric set of indices may be used so that datapertaining to a particular patient or a set of patients similar to aparticular patient can be readily extracted. This concept can besimilarly applied to surgeons, implant characteristics, CASS componentversions, etc.

Further details of the management of episode of care data is describedin U.S. Patent Application No. 62/783,858 filed Dec. 21, 2018 andentitled “Methods and Systems for Providing an Episode of Care,” theentirety of which is incorporated herein by reference.

Open Versus Closed Digital Ecosystems

In some embodiments, the CASS 100 is designed to operate as aself-contained or “closed” digital ecosystem. Each component of the CASS100 is specifically designed to be used in the closed ecosystem, anddata is generally not accessible to devices outside of the digitalecosystem. For example, in some embodiments, each component includessoftware or firmware that implements proprietary protocols foractivities such as communication, storage, security, etc. The concept ofa closed digital ecosystem may be desirable for a company that wants tocontrol all components of the CASS 100 to ensure that certaincompatibility, security, and reliability standards are met. For example,the CASS 100 can be designed such that a new component cannot be usedwith the CASS unless it is certified by the company.

In other embodiments, the CASS 100 is designed to operate as an “open”digital ecosystem. In these embodiments, components may be produced by avariety of different companies according to standards for activities,such as communication, storage, and security. Thus, by using thesestandards, any company can freely build an independent, compliantcomponent of the CASS platform. Data may be transferred betweencomponents using publicly available application programming interfaces(APIs) and open, shareable data formats.

To illustrate one type of recommendation that may be performed with theCASS 100, a technique for optimizing surgical parameters is disclosedbelow. The term “optimization” in this context means selection ofparameters that are optimal based on certain specified criteria. In anextreme case, optimization can refer to selecting optimal parameter(s)based on data from the entire episode of care, including anypre-operative data, the state of CASS data at a given point in time, andpost-operative goals. Moreover, optimization may be performed usinghistorical data, such as data generated during past surgeries involving,for example, the same surgeon, past patients with physicalcharacteristics similar to the current patient, or the like.

The optimized parameters may depend on the portion of the patient'sanatomy to be operated on. For example, for knee surgeries, the surgicalparameters may include positioning information for the femoral andtibial component including, without limitation, rotational alignment(e.g., varus/valgus rotation, external rotation, flexion rotation forthe femoral component, posterior slope of the tibial component),resection depths (e.g., varus knee, valgus knee), and implant type, sizeand position. The positioning information may further include surgicalparameters for the combined implant, such as overall limb alignment,combined tibiofemoral hyperextension, and combined tibiofemoralresection. Additional examples of parameters that could be optimized fora given TKA femoral implant by the CASS 100 include the following:

Exemplary Parameter Reference Recommendation (s) Size Posterior Thelargest sized implant that does not overhang medial/lateral bone edgesor overhang the anterior femur. A size that does not result inoverstuffing the patella femoral joint Implant Position - Medial/lateralcortical Center the implant Medial Lateral bone edges evenly between themedial/lateral cortical bone edges Resection Depth - Distal andposterior 6 mm of bone Varus Knee lateral Resection Depth - Distal andposterior 7 mm of bone Valgus Knee medial Rotation - Mechanical Axis 1°varus Varus/Valgus Rotation - External Transepicondylar 1° external fromthe Axis transepicondylar axis Rotation - Flexion Mechanical Axis 3°flexed

Additional examples of parameters that could be optimized for a givenTKA tibial implant by the CASS 100 include the following:

Exemplary Parameter Reference Recommendation (s) Size Posterior Thelargest sized implant that does not overhang the medial, lateral,anterior, and posterior tibial edges Implant Position Medial/lateral andCenter the implant anterior/posterior evenly between the cortical boneedges medial/lateral and anterior/posterior cortical bone edgesResection Depth - Lateral/Medial 4 mm of bone Varus Knee ResectionDepth - Lateral/Medial 5 mm of bone Valgus Knee Rotation - MechanicalAxis 1° valgus Varus/Valgus Rotation - External Tibial Anterior 1°external from the Posterior Axis tibial anterior paxis Posterior SlopeMechanical Axis 3° posterior slope

For hip surgeries, the surgical parameters may comprise femoral neckresection location and angle, cup inclination angle, cup anteversionangle, cup depth, femoral stem design, femoral stem size, fit of thefemoral stem within the canal, femoral offset, leg length, and femoralversion of the implant.

Shoulder parameters may include, without limitation, humeral resectiondepth/angle, humeral stem version, humeral offset, glenoid version andinclination, as well as reverse shoulder parameters such as humeralresection depth/angle, humeral stem version, Glenoid tilt/version,glenosphere orientation, glenosphere offset and offset direction.

Various conventional techniques exist for optimizing surgicalparameters. However, these techniques are typically computationallyintensive and, thus, parameters often need to be determinedpre-operatively. As a result, the surgeon is limited in his or herability to make modifications to optimized parameters based on issuesthat may arise during surgery. Moreover, conventional optimizationtechniques typically operate in a “black box” manner with little or noexplanation regarding recommended parameter values. Thus, if the surgeondecides to deviate from a recommended parameter value, the surgeontypically does so without a full understanding of the effect of thatdeviation on the rest of the surgical workflow, or the impact of thedeviation on the patient's post-surgery quality of life.

Operative Patient Care System

The general concepts of optimization may be extended to the entireepisode of care using an Operative Patient Care System 620 that uses thesurgical data, and other data from the Patient 605 and HealthcareProfessionals 630 to optimize outcomes and patient satisfaction asdepicted in FIG. 6 .

Conventionally, pre-operative diagnosis, pre-operative surgicalplanning, intra-operative execution of a prescribed plan, andpost-operative management of total joint arthroplasty are based onindividual experience, published literature, and training knowledgebases of surgeons (ultimately, tribal knowledge of individual surgeonsand their ‘network’ of peers and journal publications) and their nativeability to make accurate intra-operative tactile discernment of“balance” and accurate manual execution of planar resections usingguides and visual cues. This existing knowledge base and execution islimited with respect to the outcomes optimization offered to patientsneeding care. For example, limits exist with respect to accuratelydiagnosing a patient to the proper, least-invasive prescribed care;aligning dynamic patient, healthcare economic, and surgeon preferenceswith patient-desired outcomes; executing a surgical plan resulting inproper bone alignment and balance, etc.; and receiving data fromdisconnected sources having different biases that are difficult toreconcile into a holistic patient framework. Accordingly, a data-driventool that more accurately models anatomical response and guides thesurgical plan can improve the existing approach.

The Operative Patient Care System 620 is designed to utilize patientspecific data, surgeon data, healthcare facility data, and historicaloutcome data to develop an algorithm that suggests or recommends anoptimal overall treatment plan for the patient's entire episode of care(preoperative, operative, and postoperative) based on a desired clinicaloutcome. For example, in one embodiment, the Operative Patient CareSystem 620 tracks adherence to the suggested or recommended plan, andadapts the plan based on patient/care provider performance. Once thesurgical treatment plan is complete, collected data is logged by theOperative Patient Care System 620 in a historical database. Thisdatabase is accessible for future patients and the development of futuretreatment plans. In addition to utilizing statistical and mathematicalmodels, simulation tools (e.g., LIFEMOD®) can be used to simulateoutcomes, alignment, kinematics, etc. based on a preliminary or proposedsurgical plan, and reconfigure the preliminary or proposed plan toachieve desired or optimal results according to a patient's profile or asurgeon's preferences. The Operative Patient Care System 620 ensuresthat each patient is receiving personalized surgical and rehabilitativecare, thereby improving the chance of successful clinical outcomes andlessening the economic burden on the facility associated with near-termrevision.

In some embodiments, the Operative Patient Care System 620 employs adata collecting and management method to provide a detailed surgicalcase plan with distinct steps that are monitored and/or executed using aCASS 100. The performance of the user(s) is calculated at the completionof each step and can be used to suggest changes to the subsequent stepsof the case plan. Case plan generation relies on a series of input datathat is stored on a local or cloud-storage database. Input data can berelated to both the current patient undergoing treatment and historicaldata from patients who have received similar treatment(s).

A Patient 605 provides inputs such as Current Patient Data 610 andHistorical Patient Data 615 to the Operative Patient Care System 620.Various methods generally known in the art may be used to gather suchinputs from the Patient 605. For example, in some embodiments, thePatient 605 fills out a paper or digital survey that is parsed by theOperative Patient Care System 620 to extract patient data. In otherembodiments, the Operative Patient Care System 620 may extract patientdata from existing information sources, such as electronic medicalrecords (EMRs), health history files, and payer/provider historicalfiles. In still other embodiments, the Operative Patient Care System 620may provide an application program interface (API) that allows theexternal data source to push data to the Operative Patient Care System.For example, the Patient 605 may have a mobile phone, wearable device,or other mobile device that collects data (e.g., heart rate, pain ordiscomfort levels, exercise or activity levels, or patient-submittedresponses to the patient's adherence with any number of pre-operativeplan criteria or conditions) and provides that data to the OperativePatient Care System 620. Similarly, the Patient 605 may have a digitalapplication on his or her mobile or wearable device that enables data tobe collected and transmitted to the Operative Patient Care System 620.

Current Patient Data 610 can include, but is not limited to, activitylevel, preexisting conditions, comorbidities, prehab performance, healthand fitness level, pre-operative expectation level (relating tohospital, surgery, and recovery), a Metropolitan Statistical Area (MSA)driven score, genetic background, prior injuries (sports, trauma, etc.),previous joint arthroplasty, previous trauma procedures, previous sportsmedicine procedures, treatment of the contralateral joint or limb, gaitor biomechanical information (back and ankle issues), levels of pain ordiscomfort, care infrastructure information (payer coverage type, homehealth care infrastructure level, etc.), and an indication of theexpected ideal outcome of the procedure.

Historical Patient Data 615 can include, but is not limited to, activitylevel, preexisting conditions, comorbidities, prehab performance, healthand fitness level, pre-operative expectation level (relating tohospital, surgery, and recovery), a MSA driven score, geneticbackground, prior injuries (sports, trauma, etc.), previous jointarthroplasty, previous trauma procedures, previous sports medicineprocedures, treatment of the contralateral joint or limb, gait orbiomechanical information (back and ankle issues), levels or pain ordiscomfort, care infrastructure information (payer coverage type, homehealth care infrastructure level, etc.), expected ideal outcome of theprocedure, actual outcome of the procedure (patient reported outcomes[PROs], survivorship of implants, pain levels, activity levels, etc.),sizes of implants used, position/orientation/alignment of implants used,soft-tissue balance achieved, etc.

Healthcare Professional(s) 630 conducting the procedure or treatment mayprovide various types of data 625 to the Operative Patient Care System620. This Healthcare Professional Data 625 may include, for example, adescription of a known or preferred surgical technique (e.g., CruciateRetaining (CR) vs Posterior Stabilized (PS), up- vs down-sizing,tourniquet vs tourniquet-less, femoral stem style, preferred approachfor THA, etc.), the level of training of the Healthcare Professional(s)630 (e.g., years in practice, fellowship trained, where they trained,whose techniques they emulate), previous success level includinghistorical data (outcomes, patient satisfaction), and the expected idealoutcome with respect to range of motion, days of recovery, andsurvivorship of the device. The Healthcare Professional Data 625 can becaptured, for example, with paper or digital surveys provided to theHealthcare Professional 630, via inputs to a mobile application by theHealthcare Professional, or by extracting relevant data from EMRs. Inaddition, the CASS 100 may provide data such as profile data (e.g., aPatient Specific Knee Instrument Profile) or historical logs describinguse of the CASS during surgery.

Information pertaining to the facility where the procedure or treatmentwill be conducted may be included in the input data. This data caninclude, without limitation, the following: Ambulatory Surgery Center(ASC) vs hospital, facility trauma level, Comprehensive Care for JointReplacement Program (CJR) or bundle candidacy, a MSA driven score,community vs metro, academic vs non-academic, postoperative networkaccess (Skilled Nursing Facility [SNF] only, Home Health, etc.),availability of medical professionals, implant availability, andavailability of surgical equipment.

These facility inputs can be captured by, for example and withoutlimitation, Surveys (Paper/Digital), Surgery Scheduling Tools (e.g.,apps, Websites, Electronic Medical Records [EMRs], etc.), Databases ofHospital Information (on the Internet), etc. Input data relating to theassociated healthcare economy including, but not limited to, thesocioeconomic profile of the patient, the expected level ofreimbursement the patient will receive, and if the treatment is patientspecific may also be captured.

These healthcare economic inputs can be captured by, for example andwithout limitation, Surveys (Paper/Digital), Direct Payer Information,Databases of Socioeconomic status (on the Internet with zip code), etc.Finally, data derived from simulation of the procedure is captured.Simulation inputs include implant size, position, and orientation.Simulation can be conducted with custom or commercially availableanatomical modeling software programs (e.g., LIFEMOD®, AnyBody, orOpenSIM). It is noted that the data inputs described above may not beavailable for every patient, and the treatment plan will be generatedusing the data that is available.

Prior to surgery, the Patient Data 610, 615 and Healthcare ProfessionalData 625 may be captured and stored in a cloud-based or online database(e.g., the Surgical Data Server 180 shown in FIG. 5C). Informationrelevant to the procedure is supplied to a computing system via wirelessdata transfer or manually with the use of portable media storage. Thecomputing system is configured to generate a case plan for use with aCASS 100. Case plan generation will be described hereinafter. It isnoted that the system has access to historical data from previouspatients undergoing treatment, including implant size, placement, andorientation as generated by a computer-assisted, patient-specific kneeinstrument (PSKI) selection system, or automatically by the CASS 100itself. To achieve this, case log data is uploaded to the historicaldatabase by a surgical sales rep or case engineer using an onlineportal. In some embodiments, data transfer to the online database iswireless and automated.

Historical data sets from the online database are used as inputs to amachine learning model such as, for example, a recurrent neural network(RNN) or other form of artificial neural network. As is generallyunderstood in the art, an artificial neural network functions similar toa biologic neural network and is comprised of a series of nodes andconnections. The machine learning model is trained to predict one ormore values based on the input data. For the sections that follow, it isassumed that the machine learning model is trained to generate predictorequations. These predictor equations may be optimized to determine theoptimal size, position, and orientation of the implants to achieve thebest outcome or satisfaction level.

Once the procedure is complete, all patient data and available outcomedata, including the implant size, position and orientation determined bythe CASS 100, are collected and stored in the historical database. Anysubsequent calculation of the target equation via the RNN will includethe data from the previous patient in this manner, allowing forcontinuous improvement of the system.

In addition to, or as an alternative to determining implant positioning,in some embodiments, the predictor equation and associated optimizationcan be used to generate the resection planes for use with a PSKI system.When used with a PSKI system, the predictor equation computation andoptimization are completed prior to surgery. Patient anatomy isestimated using medical image data (x-ray, CT, MRI). Global optimizationof the predictor equation can provide an ideal size and position of theimplant components. Boolean intersection of the implant components andpatient anatomy is defined as the resection volume. PSKI can be producedto remove the optimized resection envelope. In this embodiment, thesurgeon cannot alter the surgical plan intraoperatively.

The surgeon may choose to alter the surgical case plan at any time priorto or during the procedure. If the surgeon elects to deviate from thesurgical case plan, the altered size, position, and/or orientation ofthe component(s) is locked, and the global optimization is refreshedbased on the new size, position, and/or orientation of the component(s)(using the techniques previously described) to find the new idealposition of the other component(s) and the corresponding resectionsneeded to be performed to achieve the newly optimized size, positionand/or orientation of the component(s). For example, if the surgeondetermines that the size, position and/or orientation of the femoralimplant in a TKA needs to be updated or modified intraoperatively, thefemoral implant position is locked relative to the anatomy, and the newoptimal position of the tibia will be calculated (via globaloptimization) considering the surgeon's changes to the femoral implantsize, position and/or orientation. Furthermore, if the surgical systemused to implement the case plan is robotically assisted (e.g., as withNAVIO® or the MAKO Rio), bone removal and bone morphology during thesurgery can be monitored in real time. If the resections made during theprocedure deviate from the surgical plan, the subsequent placement ofadditional components may be optimized by the processor taking intoaccount the actual resections that have already been made.

FIG. 7A illustrates how the Operative Patient Care System 620 may beadapted for performing case plan matching services. In this example,data is captured relating to the current patient 610 and is compared toall or portions of a historical database of patient data and associatedoutcomes 615. For example, the surgeon may elect to compare the plan forthe current patient against a subset of the historical database. Data inthe historical database can be filtered to include, for example, onlydata sets with favorable outcomes, data sets corresponding to historicalsurgeries of patients with profiles that are the same or similar to thecurrent patient profile, data sets corresponding to a particularsurgeon, data sets corresponding to a particular element of the surgicalplan (e.g., only surgeries where a particular ligament is retained), orany other criteria selected by the surgeon or medical professional. If,for example, the current patient data matches or is correlated with thatof a previous patient who experienced a good outcome, the case plan fromthe previous patient can be accessed and adapted or adopted for use withthe current patient. The predictor equation may be used in conjunctionwith an intra-operative algorithm that identifies or determines theactions associated with the case plan. Based on the relevant and/orpreselected information from the historical database, theintra-operative algorithm determines a series of recommended actions forthe surgeon to perform. Each execution of the algorithm produces thenext action in the case plan. If the surgeon performs the action, theresults are evaluated. The results of the surgeon's performing theaction are used to refine and update inputs to the intra-operativealgorithm for generating the next step in the case plan. Once the caseplan has been fully executed all data associated with the case plan,including any deviations performed from the recommended actions by thesurgeon, are stored in the database of historical data. In someembodiments, the system utilizes preoperative, intraoperative, orpostoperative modules in a piecewise fashion, as opposed to the entirecontinuum of care. In other words, caregivers can prescribe anypermutation or combination of treatment modules including the use of asingle module. These concepts are illustrated in FIG. 7B and can beapplied to any type of surgery utilizing the CASS 100.

Surgery Process Display

As noted above with respect to FIGS. 1 and 5A-5C, the various componentsof the CASS 100 generate detailed data records during surgery. The CASS100 can track and record various actions and activities of the surgeonduring each step of the surgery and compare actual activity to thepre-operative or intraoperative surgical plan. In some embodiments, asoftware tool may be employed to process this data into a format wherethe surgery can be effectively “played-back.” For example, in oneembodiment, one or more GUIs may be used that depict all of theinformation presented on the Display 125 during surgery. This can besupplemented with graphs and images that depict the data collected bydifferent tools. For example, a GUI that provides a visual depiction ofthe knee during tissue resection may provide the measured torque anddisplacement of the resection equipment adjacent to the visual depictionto better provide an understanding of any deviations that occurred fromthe planned resection area. The ability to review a playback of thesurgical plan or toggle between different phases of the actual surgeryvs. the surgical plan could provide benefits to the surgeon and/orsurgical staff, allowing such persons to identify any deficiencies orchallenging phases of a surgery so that they can be modified in futuresurgeries. Similarly, in academic settings, the aforementioned GUIs canbe used as a teaching tool for training future surgeons and/or surgicalstaff. Additionally, because the data set effectively records manyelements of the surgeon's activity, it may also be used for otherreasons (e.g., legal or compliance reasons) as evidence of correct orincorrect performance of a particular surgical procedure.

Over time, as more and more surgical data is collected, a rich libraryof data may be acquired that describes surgical procedures performed forvarious types of anatomy (knee, shoulder, hip, etc.) by differentsurgeons for different patients. Moreover, information such as implanttype and dimension, patient demographics, etc. can further be used toenhance the overall dataset. Once the dataset has been established, itmay be used to train a machine learning model (e.g., RNN) to makepredictions of how surgery will proceed based on the current state ofthe CASS 100.

Training of the machine learning model can be performed as follows. Theoverall state of the CASS 100 can be sampled over a plurality of timeperiods for the duration of the surgery. The machine learning model canthen be trained to translate a current state at a first time period to afuture state at a different time period. By analyzing the entire stateof the CASS 100 rather than the individual data items, any causaleffects of interactions between different components of the CASS 100 canbe captured. In some embodiments, a plurality of machine learning modelsmay be used rather than a single model. In some embodiments, the machinelearning model may be trained not only with the state of the CASS 100,but also with patient data (e.g., captured from an EMR) and anidentification of members of the surgical staff. This allows the modelto make predictions with even greater specificity. Moreover, it allowssurgeons to selectively make predictions based only on their ownsurgical experiences if desired.

In some embodiments, predictions or recommendations made by theaforementioned machine learning models can be directly integrated intothe surgical workflow. For example, in some embodiments, the SurgicalComputer 150 may execute the machine learning model in the backgroundmaking predictions or recommendations for upcoming actions or surgicalconditions. A plurality of states can thus be predicted or recommendedfor each period. For example, the Surgical Computer 150 may predict orrecommend the state for the next 5 minutes in 30 second increments.Using this information, the surgeon can utilize a “process display” viewof the surgery that allows visualization of the future state. Forexample, FIG. 7C depicts a series of images that may be displayed to thesurgeon depicting the implant placement interface. The surgeon can cyclethrough these images, for example, by entering a particular time intothe display 125 of the CASS 100 or instructing the system to advance orrewind the display in a specific time increment using a tactile, oral,or other instruction. In one embodiment, the process display can bepresented in the upper portion of the surgeon's field of view in the ARHMD. In some embodiments, the process display can be updated inreal-time. For example, as the surgeon moves resection tools around theplanned resection area, the process display can be updated so that thesurgeon can see how his or her actions are affecting the other factorsof the surgery.

In some embodiments, rather than simply using the current state of theCASS 100 as an input to the machine learning model, the inputs to themodel may include a planned future state. For example, the surgeon mayindicate that he or she is planning to make a particular bone resectionof the knee joint. This indication may be entered manually into theSurgical Computer 150 or the surgeon may verbally provide theindication. The Surgical Computer 150 can then produce a film stripshowing the predicted effect of the cut on the surgery. Such a filmstrip can depict over specific time increments how the surgery will beaffected, including, for example, changes in the patient's anatomy,changes to implant position and orientation, and changes regardingsurgical intervention and instrumentation, if the contemplated course ofaction were to be performed. A surgeon or medical professional caninvoke or request this type of film strip at any point in the surgery topreview how a contemplated course of action would affect the surgicalplan if the contemplated action were to be carried out.

It should be further noted that, with a sufficiently trained machinelearning model and robotic CASS, various elements of the surgery can beautomated such that the surgeon only needs to be minimally involved, forexample, by only providing approval for various steps of the surgery.For example, robotic control using arms or other means can be graduallyintegrated into the surgical workflow over time with the surgeon slowlybecoming less and less involved with manual interaction versus robotoperation. The machine learning model in this case can learn whatrobotic commands are required to achieve certain states of theCASS-implemented plan. Eventually, the machine learning model may beused to produce a film strip or similar view or display that predictsand can preview the entire surgery from an initial state. For example,an initial state may be defined that includes the patient information,the surgical plan, implant characteristics, and surgeon preferences.Based on this information, the surgeon could preview an entire surgeryto confirm that the CASS-recommended plan meets the surgeon'sexpectations and/or requirements. Moreover, because the output of themachine learning model is the state of the CASS 100 itself, commands canbe derived to control the components of the CASS to achieve eachpredicted state. In the extreme case, the entire surgery could thus beautomated based on just the initial state information.

Using the Point Probe to Acquire High-Resolution of Key Areas During HipSurgeries

Use of the point probe is described in U.S. patent application Ser. No.14/955,742 entitled “Systems and Methods for Planning and PerformingImage Free Implant Revision Surgery,” the entirety of which isincorporated herein by reference. Briefly, an optically tracked pointprobe may be used to map the actual surface of the target bone thatneeds a new implant. Mapping is performed after removal of the defectiveor worn-out implant, as well as after removal of any diseased orotherwise unwanted bone. A plurality of points is collected on the bonesurfaces by brushing or scraping the entirety of the remaining bone withthe tip of the point probe. This is referred to as tracing or “painting”the bone. The collected points are used to create a three-dimensionalmodel or surface map of the bone surfaces in the computerized planningsystem. The created 3D model of the remaining bone is then used as thebasis for planning the procedure and necessary implant sizes. Analternative technique that uses X-rays to determine a 3D model isdescribed in U.S. patent application Ser. No. 16/387,151, filed Apr. 17,2019 and entitled “Three-Dimensional Selective Bone Matching” and U.S.patent application Ser. No. 16/789,930, filed Feb. 13, 2020 and entitled“Three-Dimensional Selective Bone Matching,” the entirety of each ofwhich is incorporated herein by reference.

For hip applications, the point probe painting can be used to acquirehigh resolution data in key areas such as the acetabular rim andacetabular fossa. This can allow a surgeon to obtain a detailed viewbefore beginning to ream. For example, in one embodiment, the pointprobe may be used to identify the floor (fossa) of the acetabulum. As iswell understood in the art, in hip surgeries, it is important to ensurethat the floor of the acetabulum is not compromised during reaming so asto avoid destruction of the medial wall. If the medial wall wereinadvertently destroyed, the surgery would require the additional stepof bone grafting. With this in mind, the information from the pointprobe can be used to provide operating guidelines to the acetabularreamer during surgical procedures. For example, the acetabular reamermay be configured to provide haptic feedback to the surgeon when he orshe reaches the floor or otherwise deviates from the surgical plan.Alternatively, the CASS 100 may automatically stop the reamer when thefloor is reached or when the reamer is within a threshold distance.

As an additional safeguard, the thickness of the area between theacetabulum and the medial wall could be estimated. For example, once theacetabular rim and acetabular fossa has been painted and registered tothe pre-operative 3D model, the thickness can readily be estimated bycomparing the location of the surface of the acetabulum to the locationof the medial wall. Using this knowledge, the CASS 100 may providealerts or other responses in the event that any surgical activity ispredicted to protrude through the acetabular wall while reaming.

The point probe may also be used to collect high resolution data ofcommon reference points used in orienting the 3D model to the patient.For example, for pelvic plane landmarks like the ASIS and the pubicsymphysis, the surgeon may use the point probe to paint the bone torepresent a true pelvic plane. Given a more complete view of theselandmarks, the registration software has more information to orient the3D model.

The point probe may also be used to collect high-resolution datadescribing the proximal femoral reference point that could be used toincrease the accuracy of implant placement. For example, therelationship between the tip of the Greater Trochanter (GT) and thecenter of the femoral head is commonly used as reference point to alignthe femoral component during hip arthroplasty. The alignment is highlydependent on proper location of the GT; thus, in some embodiments, thepoint probe is used to paint the GT to provide a high-resolution view ofthe area. Similarly, in some embodiments, it may be useful to have ahigh-resolution view of the Lesser Trochanter (LT). For example, duringhip arthroplasty, the Dorr Classification helps to select a stem thatwill maximize the ability of achieving a press-fit during surgery toprevent micromotion of femoral components post-surgery and ensureoptimal bony ingrowth. As is generated understood in the art, the DorrClassification measures the ratio between the canal width at the LT andthe canal width 10 cm below the LT. The accuracy of the classificationis highly dependent on the correct location of the relevant anatomy.Thus, it may be advantageous to paint the LT to provide ahigh-resolution view of the area.

In some embodiments, the point probe is used to paint the femoral neckto provide high-resolution data that allows the surgeon to betterunderstand where to make the neck cut. The navigation system can thenguide the surgeon as they perform the neck cut. For example, asunderstood in the art, the femoral neck angle is measured by placing oneline down the center of the femoral shaft and a second line down thecenter of the femoral neck. Thus, a high-resolution view of the femoralneck (and possibly the femoral shaft as well) would provide a moreaccurate calculation of the femoral neck angle.

High-resolution femoral head neck data also could be used for anavigated resurfacing procedure where the software/hardware aids thesurgeon in preparing the proximal femur and placing the femoralcomponent. As is generally understood in the art, during hipresurfacing, the femoral head and neck are not removed; rather, the headis trimmed and capped with a smooth metal covering. In this case, itwould be advantageous for the surgeon to paint the femoral head and capso that an accurate assessment of their respective geometries can beunderstood and used to guide trimming and placement of the femoralcomponent.

Registration of Pre-Operative Data to Patient Anatomy Using the PointProbe

As noted above, in some embodiments, a 3D model is developed during thepre-operative stage based on 2D or 3D images of the anatomical area ofinterest. In such embodiments, registration between the 3D model and thesurgical site is performed prior to the surgical procedure. Theregistered 3D model may be used to track and measure the patient'sanatomy and surgical tools intraoperatively.

During the surgical procedure, landmarks are acquired to facilitateregistration of this pre-operative 3D model to the patient's anatomy.For knee procedures, these points could comprise the femoral headcenter, distal femoral axis point, medial and lateral epicondyles,medial and lateral malleolus, proximal tibial mechanical axis point, andtibial A/P direction. For hip procedures these points could comprise theanterior superior iliac spine (ASIS), the pubic symphysis, points alongthe acetabular rim and within the hemisphere, the greater trochanter(GT), and the lesser trochanter (LT).

In a revision surgery, the surgeon may paint certain areas that containanatomical defects to allow for better visualization and navigation ofimplant insertion. These defects can be identified based on analysis ofthe pre-operative images. For example, in one embodiment, eachpre-operative image is compared to a library of images showing “healthy”anatomy (i.e., without defects). Any significant deviations between thepatient's images and the healthy images can be flagged as a potentialdefect. Then, during surgery, the surgeon can be warned of the possibledefect via a visual alert on the display 125 of the CASS 100. Thesurgeon can then paint the area to provide further detail regarding thepotential defect to the Surgical Computer 150.

In some embodiments, the surgeon may use a non-contact method forregistration of bony anatomy intra-incision. For example, in oneembodiment, laser scanning is employed for registration. A laser stripeis projected over the anatomical area of interest and the heightvariations of the area are detected as changes in the line. Othernon-contact optical methods, such as white light interferometry orultrasound, may alternatively be used for surface height measurement orto register the anatomy. For example, ultrasound technology may bebeneficial where there is soft tissue between the registration point andthe bone being registered (e.g., ASIS, pubic symphysis in hipsurgeries), thereby providing for a more accurate definition of anatomicplanes.

Fiducial Marker Assembly for Optical Tracking

As discussed herein, surgical procedures often utilize fiducial markerscomprising light emitting diodes (LEDs) to track the location of anobject of interest, e.g., a patient bone or a surgical instrument. TheLED emits light to be tracked by an optical tracking device and acomputing device may determine the location of the object of interestbased on continuous monitoring of the emitted light. It would beadvantageous to have fiducial markers that are configured for long termuse, however standard LED housings are not suitable in this regard dueto the use of autoclaving in typical sterilization procedures betweenuses. Autoclaving includes temperature cycles that place largemechanical stresses on the housing and may result in cracks in thehousing. Further, steam cycles involved in autoclaving may lead toelectrical failures, especially where the seal of the housing isbreached. Transparency of the exit window also degrades due to thetemperature and steam cycles, thus affecting metrological performance.

Referring now to FIGS. 9A-9B, an illustrative fiducial marker fortracking an object during a surgical procedure is depicted in accordancewith an embodiment. The fiducial marker 900 may be a light emittingdiode designed and configured to be autoclaved in accordance withstandard medical sterilization procedures. The fiducial marker 900 maycomprise an opaque housing 905, a window panel 910, a metallized coating915, and a light emitting semiconductor die 920. The light emittingsemiconductor die 920 may be connected to an anode 925 and a cathode 930(e.g., via bond wires 935) that extend through a portion of the opaquehousing 905. In some embodiments, the fiducial marker 900 furthercomprises a support rod 940 for supporting the light emittingsemiconductor die 920.

FIG. 9A illustrates a side view of the fiducial marker 900. As depicted,the opaque housing 905 may include a base 905A and a peripheral wall905B that define an interior cavity 905C. In some embodiments, theopaque housing 905 is substantially cylindrical. As shown in the topview of the fiducial marker 900 in FIG. 9B, the peripheral wall 905B mayform a hollow circular cross-section. In additional embodiments, theopaque housing 905 may form another shape. In some embodiments, the base905A and peripheral wall 905B are formed as a unitary body. However, inadditional embodiments, the base 905A and the peripheral wall 905B areformed as separate components. For example, the base 905A and theperipheral wall 905B may be formed from the same material or differentmaterials and may be joined to form a fluid-tight seal capable ofwithstanding conditions associated with autoclaving. The base 905A andperipheral wall 905B may be joined by any technique known to a personhaving an ordinary level of skill in the art.

In some embodiments, the opaque housing 905 or individual componentsthereof comprise a material configured to be sealed to the window panel910. For example, where the window panel 910 is formed from a glass, theopaque housing 905 may be formed from Kovar, a nickel-cobalt ferrousalloy available from CRS Holdings, Inc. of Delaware, USA. Kovar isconfigured to have thermal expansion characteristics similar to glass inorder to allow a tight mechanical joint to be formed between the Kovarmaterial and glass, thereby avoiding stressing or cracking of the joint.The Kovar material of the opaque housing 905 may also be tailored oroptimized to match the thermal expansion characteristics of the materialof the window panel 910. For example, the material and/or constructionof the opaque housing 905 may be configured to optimize a thermalexpansion coefficient of the opaque housing. In some embodiments, theopaque housing 905 or individual components thereof may compriseadditional or alternative materials having adjustable thermal expansioncharacteristics and/or being capable of forming a tight mechanical jointwith the window panel 910.

In some embodiments, the anode 925 and the cathode 930 extend throughthe base 905A. For example, as shown in FIGS. 9A-9B, the anode 925 andcathode 930 may each comprise a cylindrical rod extending through thebase 905A. In some embodiments, the anode 925 is oriented parallel tothe cathode 930. However, additional shapes and configurations of theanode 925 and cathode 930 are contemplated herein. In some embodiments,the anode 925 and/or the cathode 930 may be alternatively arranged onother portions of the opaque housing, e.g., the peripheral wall 905B.The anode 925 and cathode 930 may be formed as separate components fromthe base opaque housing 905. For example, the anode 925 and cathode 930may be formed from a different material than the opaque housing 905 andmay be joined to form a fluid-tight seal capable of withstandingconditions associated with autoclaving. The anode 925 and cathode 930may be joined to the opaque housing 905 by any technique known to aperson having an ordinary level of skill in the art.

Referring once again to FIGS. 9A-9B, the window panel 910 is joined tothe opaque housing 905 to enclose the interior cavity 905C. For example,the window panel 910 may be joined to an end of the peripheral wall 905Bopposite the base 905A. However, alternative configurations arecontemplated within the scope of this disclosure. As depicted in FIG.9B, the window panel 910 may be transparent in order to transmit lighttherethrough. In some embodiments, the window panel 910 is fully orsubstantially transparent in order to minimize scattering and/orreflection of light as it passes through the window panel. However, insome embodiments, the window panel 910 may be configured assemi-transparent or translucent. In some embodiments, the window panel910 is a flat panel in order to simplify the optical effects on emittedlight.

In some embodiments, the window panel 910 is formed as a glass from avariety of materials. In some embodiments, the window panel 910comprises aluminum oxide. In some embodiments, the window panel 910comprises aluminum(I) oxide (Al₂O), aluminum(II) oxide (AlO), and/oraluminum(III) oxide (Al₂O₃). The aluminum oxide(s) for the window panel910 may be provided in a variety of forms. For example, the aluminumoxide(s) may comprise alumina and/or corundum (e.g., sapphire, ruby, andthe like). Additional or alternative materials may be used to form thewindow panel 910 to improve various characteristics of the window panel910 as would be known to a person having any ordinary level of skill inthe art.

In some embodiments, the material and/or construction of the windowpanel 910 is configured to optimize thermal expansion characteristics ofthe window panel 910. For example, the material and/or construction ofthe window panel 910 may be configured to optimize a thermal expansioncoefficient of the window panel 910. In some embodiments, the windowpanel 910 is configured to have thermal expansion characteristicssimilar to the opaque housing 905 in order to minimize the effects ofautoclaving on the construction of the fiducial marker 900. Where thethermal expansion characteristics of the components of the fiducialmarker 900 are similar, the effects of the autoclaving process on thestructure of the fiducial marker 900 (e.g., stresses, cracks, and thelike) may be reduced or minimized. In some embodiments, the window panel910 is configured to have thermal expansion characteristics similar toone or more individual components of the opaque housing, e.g., theperipheral wall 905B to which the window panel 910 is joined.

The window panel 910 may have a thickness configured to reducerefraction and/or scattering of light passing through the window panel910. In some embodiments, the window panel 910 has a thickness of 20 mm,15 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1 mm, lessthan 1 mm, or individual values or ranges therebetween. A reducedthickness of the window panel 910 may result in reduced refractionand/or scattering of light passing through the window panel 910, thussimplifying the optical corrections to be performed by the system asfurther discussed herein.

Referring once again to FIG. 9A, a metallized coating 915 is provided atan interface of the opaque housing 905 and the window panel 910 to fusethe opaque housing 905 and the window panel 910 and form a fluid-tightseal (i.e., hermetic seal) therebetween. In some embodiments, themetallized coating 915 is a material that blocks and/or absorbs light.In some embodiments, the metallized coating 915 covers the entireinterface between the opaque housing 905 and the window panel 910 suchthat the opaque housing 905 and the window panel 910 do not directlycontact one another. For example, as shown in cross-section in FIG. 9A,the metalized coating covers the entire depicted surface of theinterface. In some embodiments, the metalized coating 915 covers only aportion of the interface between the opaque housing 905 and the windowpanel 910, e.g., a radially inward portion of the interface.

Further, the metallized coating 915 may extend about the entireperimeter of the window panel 910 to completely cover the interface andform a ring about a periphery of the fiducial marker 900. Accordingly,the metallized coating 915 completely seals the opaque housing 905 andthe window panel 910 in a fluid-tight manner (i.e., hermetically sealingthe interior cavity 905C from an external environment).

In some embodiments, the metallized coating 915 comprises a soldermaterial, i.e., a fusible metal alloy configured to be melted andapplied to components to create a permanent bond. Solder material may beapplied as a metallized coating 915 using a soldering iron, solderinggun, or another tool for heating and applying the solder material. Insome embodiments, the metallized coating 915 comprises gold-tin solder.However, any solder material known to an ordinary artisan may be used,including but not limited to soft solders, hard solders, glass solders,tin-based solders (e.g., gold-tin solders, tin-lead solders, andtin-silver-copper solders), lead-based solders, indium-based solders,and lead-free solders. In some embodiments, the metallized coating 915may comprise a plurality of layers of different materials and/ordifferent types of solder.

In some embodiments, fiducial marker 900 further comprises alight-absorbing coating or layer facing the window panel 910. In someembodiments, the light-absorbing coating may be affixed to an interiorface of the window panel 910, i.e. between the window panel 910 and themetallized coating 915. Accordingly, light that reflects internallywithin the window may be absorbed by the light-absorbing coating todampen the internal reflections and prevent additional reflections offof the metallized coating 915, thereby reducing the amount ofreflections that may be detected by the system as further discussedherein. In some embodiments, the light-absorbing coating is black inorder to absorb light. However, materials of additional or alternatecolors may be used to absorb light. In some embodiments, thelight-absorbing coating may be applied to the interior face of thewindow panel 910 prior to applying the metallized coating 915. However,the light-absorbing coating may be applied to a variety of additional oralternate surfaces in a variety of manners.

As shown in FIGS. 9A-9B, the light emitting semiconductor die 920 may bepositioned within the interior cavity 905C. For example, as depicted inFIG. 9B, the light emitting semiconductor die may be positionedcentrally with respect to the peripheral wall 905B. The light emittingsemiconductor die 920 may be connected to the anode 925 and the cathode930, e.g., by bond wires 935. However, alternative means for connectingthe light emitting semiconductor die 920 to the anode 925 and thecathode 930 are contemplated herein.

In some embodiments, the light emitting semiconductor die 920 ispositioned proximate to the window panel 910 to emit light through thewindow panel 910 and reduce reflection of light from the light emittingsemiconductor die 920 within the fiducial marker 900. For example, wherethe distance of the light emitting semiconductor die 920 from the windowpanel 910 is increased, the amount of light emitted from the lightemitting semiconductor die 920 upon the base 905A and/or the peripheralwall 905B increases accordingly and may reflect off of these surfaces indifferent directions including through the window panel 910. Further,where the distance of the light emitting semiconductor die 920 from thewindow panel 910 is increased, the amount of light emitted from thelight emitting semiconductor die 920 that reaches a peripheral edge ofthe window panel 910 (e.g., left and right lateral sides or edges of thewindow panel 910 as seen in FIG. 9A) increases accordingly and mayreflect back into the housing and/or undergo multiple reflections withinthe window. Accordingly, reducing the distance of the light emittingsemiconductor die 920 from the window panel 910 reduces internal lightreflection, thereby simplifying the optical corrections to be performedby the system as further discussed herein.

In some embodiments, the support rod 940 supports the light emittingsemiconductor die 920 in a position proximate the window panel 910. Insome embodiments, the height of the support rod 940 is configured tominimize a distance between the light emitting semiconductor die 920 andthe window panel 910. However, the height of the support rod 940 mayvary. In some embodiments, the support rod 940 has a diameter matched toa diameter of the light emitting semiconductor die 920. In someembodiments, the support rod 940 has a diameter slightly greater thanthe diameter of the light emitting semiconductor die 920. In someembodiments, the support rod 940 has a diameter substantially equal tothe diameter of the light emitting semiconductor die 920. In someembodiments, the support rod 940 has a diameter less than a diameter ofthe light emitting semiconductor die 920. By decreasing the diameter ofthe support rod 940, the amount of light reaching and/or reflecting offof the support rod 940 (e.g., light emitted from the light emittingsemiconductor die 920) may be further reduced, thus simplifying theoptical corrections to be performed by the system as further discussedherein.

The support rod 940 may be formed from a variety of materials. In someembodiments, the support rod 940 is formed from any of the materialsdescribed with respect to the opaque housing 905. For example, thesupport rod 940 may be formed from the same material as the base 905Aand/or the peripheral wall 905B. In some embodiments, the support rod940 may be formed from a heat conducting material. Accordingly, thesupport rod 940 may further function as a heat sink to dissipate heatthat accumulates at the light emitting semiconductor die 920. In someembodiments, the support rod 940 may be formed from a materialconfigured for use as one of an anode and a cathode. Accordingly, thesupport rod 940 may replace one of the anode 925 and the cathode 930 orbe configured as an extension of one of the anode 925 and the cathode930. In embodiments where the support rod 940 is configured as one ofthe anode 925 and the cathode 930 or an extension thereof, the means ofconnection to the anode 925 and cathode 930 may be altered accordingly.In some embodiments, where the support rod 940 serves as the anode 925,the light emitting semiconductor die 920 may be directly connected tothe support rod 940 without the use of a bond wire 935 and may beconnected to the cathode 930 through a bond wire 935. In someembodiments, where the support rod 940 serves as the anode 925, a bondwire 935 may nonetheless be used to connect the light emittingsemiconductor die 920 to the support rod 940. For example, a bond wire935 may connect the light emitting semiconductor die 920 (at the top ofthe support rod 940) to a portion of the support rod 940 near the base905A.

Referring now to FIG. 10 , a partial side view of an alternate fiducialmarker for tracking an object during a surgical procedure is depicted inaccordance with an embodiment. The fiducial marker 1000 may be a lightemitting diode designed and configured to be autoclaved in accordancewith standard medical sterilization procedures. Similar to the fiducialmarker 900 of FIGS. 9A-9B, the fiducial marker 1000 may comprise anopaque housing 1005 (e.g., a base 1005A, a peripheral wall 1005B, and aninterior cavity 1005C), a window panel 1010, a metallized coating 1015,a light emitting semiconductor die 1020, an anode 1025 and a cathode1030 connected to the light emitting semiconductor die 1020 via bondwires 1035, and a support rod 1040 for supporting the light emittingsemiconductor die 1020. In some embodiments, fiducial marker 1000further comprises a light-absorbing coating or layer facing the windowpanel 1010 as described herein, e.g., a black material affixed to aninterior face of the window panel 1010. The fiducial marker 1000 mayfurther include features and configurations as depicted and describedwith respect to the fiducial marker 900 of FIGS. 9A-9B except asdifferentiated herein. The peripheral wall 1005B may include a notch1045 on a radially inward facing surface of the peripheral wall 1005Bthat defines the interface of the opaque housing 1005 and the windowpanel 1010. The notch 1045 may be configured to receive a portion of thewindow panel 1010 therein in order to form a stable interface betweenthe opaque housing 1005 and the window panel 1010. As shown, themetallized coating 1015 at the interface of the opaque housing 1005 andthe window panel 1010 may cover the entire interface (i.e., the entiresurface of the notch 1045) including a horizontal portion and a verticalportion of the interface. The notch 1045 provides a mated joint betweenthe opaque housing 1005 and the window panel 1010 and additionallyincreases the surface area of the interface that may be fused by themetallized coating 1015, thereby providing a more stable joint. However,in some embodiments, the metalized coating 1015 may cover only a portionof the interface, e.g., a horizontal portion of the interface.

Referring now to FIGS. 11A-11B, a partial side view (FIG. 11A) and a topview (FIG. 11B) of an alternate embodiment of a fiducial marker fortracking an object during a surgical procedure is depicted in accordancewith an embodiment. The fiducial marker 1100 may be a light emittingdiode designed and configured to be autoclaved in accordance withstandard medical sterilization procedures. Similar to the fiducialmarker 1000 of FIG. 10 , the fiducial marker 1100 may comprise an opaquehousing 1105 (e.g., a base (not shown), a peripheral wall 1105B, and aninterior cavity 1105C), a window panel 1110, a metallized coating 1115,a light emitting semiconductor die 1120, an anode 1125 and a cathode1130 connected to the light emitting semiconductor die 1120 via bondwires 1135, a support rod 1140 for supporting the light emittingsemiconductor die 1120, and a notch 1145 on the peripheral wall 1105Bfor receiving the window panel 1110. In some embodiments, fiducialmarker 1100 further comprises a light-absorbing coating or layer facingthe window panel 1110 as described herein, e.g., a black materialaffixed to an interior face of the window panel 1110. The fiducialmarker 1100 may further include features and configurations as depictedand described with respect to fiducial marker 900 and/or fiducial marker1000 except as differentiated herein. The window panel 1110 may includea notch 1150 on a upper peripheral surface of the window panel 1110. Thenotch 1150 may be configured to mate with a portion of a marker support1155 to secure the fiducial marker 1100 thereto. The mating of the notch1150 with the marker support 1155 clamps the fiducial marker into themarker support 1155 with high mechanical stability. The marker support1155 may be a part of any device intended to be tracked by an opticaltracking system. In some embodiments, the marker support 1155 may be aportion of a surgical instrument. In some embodiments, the markersupport 1155 may be a tracking support or tracking array for attachmentto a portion of a patient anatomy (e.g., a bone) or other object ofinterest. In some embodiments, the marker support 1155 may be a trackingsupport or tracking array for attachment to a location of interest, e.g.a reference point.

In some embodiments, the metallized coating 1115 may comprise a materialthat blocks and/or absorbs light and may extend beyond the interface ofthe opaque housing 1105 and the window panel 1110. As shown in FIGS.11A-11B, the metallized coating 1115 forms a ring about the periphery ofthe window panel 1110. The ring further extends radially inwardly beyondthe interface to cover a lower surface of the window panel 1110, therebypreventing transmission of light through a portion of the window panel1110. In some embodiments, the window panel 1110 and the metallizedcoating 1115 are configured to block light from the light emittingsemiconductor die 1120 from reaching a peripheral edge of the windowpanel 1110 (e.g., left and right lateral sides or edges of the windowpanel 1110 as seen in FIG. 11A). In other words, light that would reachthe peripheral edge of the window panel 1110 is instead blocked and/orabsorbed by the metallized coating 1115, thus reducing internal lightreflection. Further, the window panel 1110 and the metallized coating1115 are configured to block light from the light emitting semiconductordie 1120 from reaching the clamping parts, i.e. the notch 1150 and themarker support 1155, thus reducing reflections of light from theclamping parts. The light may be blocked from reaching the peripheraledge of the window panel 1110, the notch 1150, and the marker support1155 by decreasing an inner diameter of the ring formed by themetallized coating 1115, thereby increasing the coverage of themetallized coating 1115 on the window panel 1110.

As shown in FIG. 11B, a widened ring of the metallized coating 1115 maycover a significant portion of the lower surface of the window panel.The window panel 1110 may also maintain an uncovered portion (i.e.,defined by the inner diameter of the ring as shown in FIG. 11B)sufficient to facilitate detection of light from the light emittingsemiconductor die 1120 from an adequately wide array of angles as isnecessary in a typical surgical procedure, e.g., as the marker support1155. In some embodiments, the ring has an inner diameter of 0.05 cm,0.1 cm, 0.2 cm, 0.3 cm, 0.4 cm, 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm,1 cm, 2 cm, 3 cm, 4 cm, 5 cm, greater than 5 cm, or individual values orranges therebetween. In some embodiments, the metallized coating 1115covers a percentage of the lower surface of the window panel 1110, suchas 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, greater than 90%, orindividual values or ranges therebetween.

In some embodiments, the fiducial marker 1100 is configured to preventlight from reaching the peripheral edge of the window panel 1110 and/orthe clamping parts based on configuration of various parameters. Forexample, the inner diameter of the ring of the metallized coating 1115,the thickness of the window panel 1110, the diameter of the window panel1110, and the distance of the light emitting semiconductor die 1120 fromthe window panel 1110 may all have an effect on the direction and reachof the light from the light emitting semiconductor die 1120.Accordingly, these parameters may together be configured to preventlight from reaching the peripheral edge of the window panel 1110 and/orthe clamping parts based on configuration of various parameters.

The disclosed embodiments of fiducial markers provide significantadvantages over conventional fiducial markers. For example, —the opticaleffects on the light from the light emitting semiconductor die aregreatly simplified to facilitate calculations as further describedherein. Further, the simple design of the window panel as well as othercomponents can be achieved in manufacturing by standard techniques withacceptable tolerance. For example, a flat window panel may bemanufactured by standard techniques, and minor variations in thicknessof the window panel and/or the metallized coating have a negligibleeffect on refraction and other optical effects. Accordingly, thesefactors do not need to be considered or accounted for during subsequentcalculations.

System for Optically Tracking an Object with a Fiducial Marker Assembly

Referring now to FIG. 12 , a block diagram of an illustrative system fortracking an object in accordance with an embodiment is depicted. In someembodiments, the system 1200 is a surgical system or a robotic surgicalsystem. As shown in FIG. 12 , the system 1200 may include a computingdevice 1205, an optical tracking device 1210, and one or more fiducialmarkers 1215. The fiducial marker 1215 may be any of the embodimentsdepicted or described herein (e.g., fiducial marker 900 of FIG. 9 ,fiducial marker 1000 of FIG. 10 , or fiducial marker 1100 of FIG. 11 ).In some embodiments, the fiducial marker 1215 is coupled to a markersupport 1220 such as a surgical instrument, a tracking support, or atracking array.

In some embodiments, the computing device 1205 is a processor, acomputing device of CASS, such as 150, or other types of computing ordata processing systems as described herein. The computing device 1205may be in electronic communication with the optical tracking device 1210to receive signals therefrom. In some embodiments, electroniccommunication between the computing device 1205 and the optical trackingdevice 1210 may be wired. In additional embodiments, electroniccommunication between the computing device 1205 and the optical trackingdevice 1210 may be through a wireless transmission system.

In some embodiments, the optical tracking device 1210 comprises two ormore optical sensors 1225 (shown in FIG. 13 ). In some embodiments, theoptical tracking device 1210 comprises more than two optical sensors1225. In some embodiments the optical sensors 1225 are cameras, althoughother CMOS or CCD sensors may be used. In some embodiments, the camerasare configured to detect light in a particular range of wavelengths. Forexample, the cameras may be configured to detect light in the near-IRspectrum, the visible spectrum, or a subset of the visible spectrum(e.g., wavelengths associated with a specific color or colors). Theoptical sensors 1225 of the optical tracking device 1210 may beconfigured to detect light emitted from the fiducial marker 1215.

In some embodiments, such as is shown in FIG. 13 , the fiducial marker1215 includes a housing 1230, a window panel 1235, and a light source1240. When the light source 1240 emits light, light rays pass throughthe window panel 1235 and exit the fiducial marker 1215. The opticalsensors 1225 each perceive a position of a light ray emitted from thelight source 1240. As demonstrated and discussed with respect to FIG. 8, the light rays from the light source 1240 may be refracted as theypass through the window panel 1235 such that the light rays do not forma continuous straight line.

Referring now to FIG. 13 , an illustrative computation of the locationof the light source with refraction correction is depicted in accordancewith an embodiment. The perceived position of each light ray 1245(depicted as a broken line in FIG. 13 ) is detected by the respectiveoptical sensor 1225 and transmitted to the computing device 1205 viaelectronic communication. The computing device 1205 calculates andapplies a refraction deviation 1250 for the position of each light ray1245, resulting in adjusted light ray positions 1255 (depicted as asolid line in FIG. 13 ) to correct for refraction. The refractiondeviation 1250 is calculated based on a refraction index of the windowpanel 1235, a thickness of the window panel 1235, and an angle of thelight ray 1245 to the window panel 1235. The angle of the light ray 1245to the window panel varies based on the orientation of the fiducialmarker 1215 with respect to each optical sensor 1225, and thus therefraction deviation 1250 may be different for each optical sensor 1225.Additional optical properties of the window panel 1235 may be includedin the refraction deviation 1250 as would be known to a person having anordinary level of skill in the art.

In some embodiments, the orientation of the fiducial marker 1215 withrespect to each optical sensor 1225 may be determined by the computingdevice 1205. For example, the optical tracking device 1210 may collectimage information related to the fiducial marker 1215 and transmit theinformation to the computing device 1205. The computing device 1205 maydetermine an orientation of the fiducial marker 1215 based on the imageinformation and a known geometry of the fiducial marker 1215. Where amarker support is used, the optical tracking device 1210 may collectimage information related to the marker support 1220 and transmit theinformation to the computing device 1205. The computing device 1205 maydetermine an orientation of the fiducial marker 1215 based on the imageinformation, a known geometry of the marker support 1220, and a knownorientation of the fiducial marker 1215 with respect to the markersupport 1220. In some embodiments, an orientation sensor such as anaccelerometer may be coupled to the fiducial marker 1215 and/or themarker support 1220, and the accelerometer may relay orientationinformation to the computing device 1205 to calculate the orientation ofthe fiducial marker. Additional types of orientation sensors as would beknown to a person having an ordinary level of skill in the art mayadditionally or alternatively be used in a similar manner. In someembodiments, additional systems and methods may be used to determine theorientation of the fiducial marker 1215 as would be apparent to a personhaving an ordinary level of skill in the art.

Based on the adjusted light ray positions 1255, the true location of thelight source 1240 may be calculated by triangulation. Without correctionfor refraction, the location of the light source 1240 may includesignificant metrological error resulting in a perceived location 1260depicted in FIG. 13 for comparison. While FIG. 13 depicts refractiondeviation and correction in two dimensions, refraction occurs in threedimensions and thus significant metrological error may exist in bothtransverse and longitudinal directions. The system 1200 and techniquesdescribed herein may correct for refraction in both transverse andlongitudinal directions.

In some embodiments, the location of the light source 1240 is calculatediteratively. For example, the computing device 1205 may determine anorientation of the fiducial marker 1215 based on the image information,a known geometry of the marker support 1220, and/or a known orientationof the fiducial marker 1215 with respect to the marker support 1220. Thecomputing device 1205 can calculate the location of the light source1240 by the techniques described herein based in part on the determinedorientation of the fiducial marker 1215. The calculated position of thelight source 1240 may be used to calculate a new value for theorientation of the fiducial marker 1215. The new value may be used in asecond iteration of the calculation of the location of the light source1240, which may provide a more accurate result. This process may berepeated for any number of iterations. In some embodiments, the processis repeated until a predetermined measure of accuracy is achieved. Forexample, the process may be repeated until a change in the determinedlocation of the light source 1240 in consecutive iterations is below apredetermined threshold.

Based on the location of the light source 1240, the location of anobject of interest connected thereto may be calculated using knownspatial relationships of the light source 1240 to the object ofinterest. For example, the light source 1240 may be a known distancefrom the object of interest based on the dimensions and orientation ofthe fiducial marker 1215, the dimensions and orientation of the markersupport 1220, and/or the location of coupling to the object of interest.In some embodiments, the system 1200 is configured to calculate thelocation of the object of interest based on an algorithm comprising thetechniques described herein. In some embodiments, the system 1200 isconfigured to calculate the location of the object of interest inreal-time. In some embodiments, the system 1200 is configured tocalculate and monitor the location of the object of interestcontinuously over a period of a time, e.g., the duration of a surgicalprocedure.

In some embodiments, the system 1200 is configured to calculate andmonitor the location of the object of interest based on multiplefiducial markers 1215 attached thereto, e.g., two, three, four, or morefiducial markers 1215. In some embodiments, multiple fiducial markers1215 may be supported by a single marker support 1220. In someembodiments, each fiducial marker 1215 may be uniquely oriented withrespect to the object of interest. When calculating the location of theobject of interest in any given instance, the system 1200 may select afiducial marker 1215 for the calculation based on the tilt angulationwith respect to the optical sensors 1225. Tilt angulation may increaselocalization error in a manner known to the computing device 1205 (e.g.,where tilt angulation is particularly high) and thus a suitable fiducialmarker 1215 for the calculation may be selected to decrease localizationerror. In some embodiments, the calculation may be performed based onmultiple fiducial markers 1215 and the calculation location from eachfiducial marker 1215 may be averaged to generate a more accurate overallcalculation of the location for the object of interest.

Referring now to FIGS. 14A-14C, an exemplary evaluation of localizationerror is illustrated in accordance with an embodiment. FIG. 14A depictslocalization error in a transverse direction, FIG. 14B depicts locationerror in a longitudinal direction, and FIG. 14C depicts a totallocalization error. In each of FIGS. 14A-14C, the solid line representslocalization error as a function of mean tilt angle without correctingfor refraction and the broken line depicts localization error as afunction of mean tilt angle with refraction correction by the techniquesdescribed herein. Without refraction correction, the localization errorrises quickly above 0.1 mm for tilt angles greater than 20°. Afterrefraction correction, a significant reduction in localization error maybe achieved up to very large tilt angles.

In some embodiments, the system 1200 further comprises one or moredisplays in wired or wireless electronic communication with thecomputing device 1205. The one or more displays may display the locationof the object of interest and/or related information to a user. In anembodiment, the one or more displays may include a digital display. Anyof the collected or calculated data described herein may be displayed toa user in real-time on the one or more displays. Further, alternate oradditional information may be provided to the user within the scope ofthis disclosure as will be apparent to those of ordinary skill in theart. In some embodiments, the display may be an external screen ormonitor, a tablet, a display of a CASS, and/or an augmented realityheadset worn by a user.

It should be noted that the metrological accuracy of the techniquesdescribed herein may be further improved by use of the fiducial markersdescribed herein. Fiducial markers 900, 1000, and 1100 providesufficiently simple designs to facilitate calculation of markerpositions with an acceptable degree of accuracy. Additionally, fiducialsmarkers 900, 1000, and 1100 include features that mitigate refractionand other optical effects in order to simplify calculations and minimizethe magnitude of correction.

Method of Optically Tracking an Object with a Fiducial Marker Assembly

Referring now to FIG. 15 , a flow diagram 1500 of an illustrative methodof tracking an object with a fiducial marker is depicted in accordancewith an embodiment. As shown in FIG. 15 , a fiducial marker comprising alight source (e.g., fiducial marker 900, fiducial marker 1000, orfiducial marker 1100) is coupled 1505 to the object. In someembodiments, a marker support may be used to couple 1505 the fiducialmarker to the object. The position of a light ray emitted by the lightsource is detected 1510 by each of a plurality of optical sensors of anoptical tracking device, and the positions of the light rays arereceived 1515 by a computing device from the optical tracking device.The position of each light ray is adjusted 1520 by the computing devicebased on a refraction deviation to obtain an adjusted position of eachlight ray. The location of the light source is triangulated 1525 basedon the adjusted position of each light ray, and the location of theobject is calculated 1530 based on the location of the light source.

In some embodiments, the method further comprises registering thefiducial marker with the computing device. For example, the light fromthe light source may be detected while the object is placed in a knownlocation such that the computing device may determine a spatialrelationship between the light source and the object. In someembodiments, the spatial relationship may be determined based on inputfrom a user. In some embodiments, the spatial relationship may bedetermined based on known parameters. For example, the light source maybe a known distance from the object based on the dimensions andorientation of the fiducial marker, the dimensions and orientation ofthe marker support, and/or the location of coupling to the object ofinterest. Additional registration or calibration procedures may beimplemented as would be apparent to a person having an ordinary level ofskill in the art.

In some embodiments, the method 1500 comprises coupling a plurality offiducial markers to the object. For example, each fiducial marker may beuniquely oriented with respect to the object. In some embodiments, themethod 1500 further comprises selecting a fiducial marker of theplurality of fiducial markers for use in the calculations based on thetilt angulation with respect to the optical sensors. Tilt angulation mayincrease localization error in a manner known to the computing deviceand thus a suitable fiducial marker may be selected to decreaselocalization error. In some embodiments, selecting a fiducial markercomprises selecting the fiducial marker having the lowest tiltangulation. In some embodiments, selecting a fiducial marker is based ona known relationship between tilt angulation and localization error.

In some embodiments, the method 1500 comprises calculating the locationof the object as described based on each of two or more fiducial markersof the plurality of fiducial markers. In some embodiments, thecalculated location of the object from each fiducial marker may beaveraged to generate a more accurate overall calculation of the locationfor the object.

In some embodiments, the method 1500 further comprises displaying thelocation of the object and/or related information on a display. In anembodiment, the one or more displays may include a digital display. Anyof the collected or calculated data described herein may be displayed toa user in real-time on the one or more displays. Further, alternate oradditional information may be provided to the user within the scope ofthis disclosure as will be apparent to those of ordinary skill in theart. In some embodiments, the display may be an external screen ormonitor, a tablet, a display of a CASS, and/or an augmented realityheadset worn by a user.

The devices, systems, and methods as described herein are not intendedto be limited in terms of the particular embodiments described, whichare intended only as illustrations of various features. Manymodifications and variations to the devices, systems, and methods can bemade without departing from their spirit and scope, as will be apparentto those skilled in the art.

Additionally, the embodiments depicted and described herein are intendedto be exemplary and do not limit the scope of the subject matter herein.It is contemplated that features or configurations described withrespect to one of the disclosed embodiments may be applied to additionaldisclosed embodiments within the scope of this disclosure.

In some embodiments, the systems and methods described herein may beused to calculate and monitor the location of multiple objects ofinterest simultaneously. In some embodiments, each object of interestcomprises one or more fiducial markers coupled thereto. In someembodiments, the fiducial markers for each object of interest aredistinguished by a recognizable pattern or arrangement of the fiducialmarkers. In some embodiments, the fiducial markers for each object ofinterest are distinguished by the wavelength of light emitted from thefiducial markers. For example, the fiducial markers for each object ofinterest may emit light of a different color or a different range ofwavelengths. Where these distinguishing characteristics are known to thecomputing device (e.g., by user input, registration, or calibrationprocedures), each object of interest may be individually trackedsimultaneously in real time.

In some embodiments, one or more components of the present disclosuremay be used independently. For example, any of the fiducial markersdescribed herein may be implemented without a system to correct forrefraction. In some embodiments, the window panel may be sufficientlythin such that refraction is negligible and location may be calculatedwith an acceptable degree of accuracy without refraction correction.Further, in some embodiments, the methods of tracking an object asdescribed herein may be used with other fiducial markers than thosedescribed.

The methods, systems, and apparatuses described herein may be utilizedin a wide variety of medical procedures where tracking of one or moreobjects may be beneficial to planning and/or executing the surgicalprocedure. As non-limiting examples, the methods, system, andapparatuses may be utilized in orthopaedic procedures including jointarthroplasties, arthroscopic procedures, spinal procedures,maxillofacial procedures, rotator cuff procedures, ligament repair andreplacement procedures, reconstructive surgery, otorhinolaryngologicalprocedures, neurological procedures, and additional types of medicalprocedures as would be apparent to a person having an ordinary level ofskill in the art.

FIG. 16 illustrates a block diagram of an illustrative data processingsystem 1600 in which embodiments are implemented. The data processingsystem 1600 is an example of a computer, such as a server or client, inwhich computer usable code or instructions implementing the process forillustrative embodiments of the present invention are located. In someembodiments, the data processing system 1600 may be a server computingdevice. For example, data processing system 1600 can be implemented in aserver or another similar computing device operably connected to asurgical system 100 as described above. The data processing system 1600can be configured to, for example, transmit and receive informationrelated to a patient and/or a related surgical plan with the surgicalsystem 100.

In the depicted example, data processing system 1600 can employ a hubarchitecture including a north bridge and memory controller hub (NB/MCH)1601 and south bridge and input/output (I/O) controller hub (SB/ICH)1602. Processing unit 1603, main memory 1604, and graphics processor1605 can be connected to the NB/MCH 1601. Graphics processor 1605 can beconnected to the NB/MCH 1601 through, for example, an acceleratedgraphics port (AGP).

In the depicted example, a network adapter 1606 connects to the SB/ICH1602. An audio adapter 1607, keyboard and mouse adapter 1608, modem1609, read only memory (ROM) 1610, hard disk drive (HDD) 1611, opticaldrive (e.g., CD or DVD) 1612, universal serial bus (USB) ports and othercommunication ports 1613, and PCI/PCIe devices 1614 may connect to theSB/ICH 1602 through bus system 1616. PCI/PCIe devices 1614 may includeEthernet adapters, add-in cards, and PC cards for notebook computers.ROM 1610 may be, for example, a flash basic input/output system (BIOS).The HDD 1611 and optical drive 1612 can use an integrated driveelectronics (IDE) or serial advanced technology attachment (SATA)interface. A super I/O (SIO) device 1615 can be connected to the SB/ICH1602.

An operating system can run on the processing unit 1603. The operatingsystem can coordinate and provide control of various components withinthe data processing system 1600. As a client, the operating system canbe a commercially available operating system. An object-orientedprogramming system, such as the Java™ programming system, may run inconjunction with the operating system and provide calls to the operatingsystem from the object-oriented programs or applications executing onthe data processing system 1600. As a server, the data processing system1600 can be an IBM® eServer™ System® running the Advanced InteractiveExecutive operating system or the Linux operating system. The dataprocessing system 1600 can be a symmetric multiprocessor (SMP) systemthat can include a plurality of processors in the processing unit 1603.Alternatively, a single processor system may be employed.

Instructions for the operating system, the object-oriented programmingsystem, and applications or programs are located on storage devices,such as the HDD 1611, and are loaded into the main memory 1604 forexecution by the processing unit 1603. The processes for embodimentsdescribed herein can be performed by the processing unit 1603 usingcomputer usable program code, which can be located in a memory such as,for example, main memory 1604, ROM 1610, or in one or more peripheraldevices.

A bus system 1616 can be comprised of one or more busses. The bus system1616 can be implemented using any type of communication fabric orarchitecture that can provide for a transfer of data between differentcomponents or devices attached to the fabric or architecture. Acommunication unit such as the modem 1609 or the network adapter 1606can include one or more devices that can be used to transmit and receivedata.

Those of ordinary skill in the art will appreciate that the hardwaredepicted in FIG. 16 may vary depending on the implementation. Otherinternal hardware or peripheral devices, such as flash memory,equivalent non-volatile memory, or optical disk drives may be used inaddition to or in place of the hardware depicted. Moreover, the dataprocessing system 1600 can take the form of any of a number of differentdata processing systems, including but not limited to, client computingdevices, server computing devices, tablet computers, laptop computers,telephone or other communication devices, personal digital assistants,and the like. Essentially, data processing system 1600 can be any knownor later developed data processing system without architecturallimitation.

While various illustrative embodiments incorporating the principles ofthe present teachings have been disclosed, the present teachings are notlimited to the disclosed embodiments. Instead, this application isintended to cover any variations, uses, or adaptations of the presentteachings and use its general principles. Further, this application isintended to cover such departures from the present disclosure as comewithin known or customary practice in the art to which these teachingspertain.

In the above detailed description, reference is made to the accompanyingdrawings, which form a part hereof. In the drawings, similar symbolstypically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the presentdisclosure are not meant to be limiting. Other embodiments may be used,and other changes may be made, without departing from the spirit orscope of the subject matter presented herein. It will be readilyunderstood that various features of the present disclosure, as generallydescribed herein, and illustrated in the Figures, can be arranged,substituted, combined, separated, and designed in a wide variety ofdifferent configurations, all of which are explicitly contemplatedherein.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various features. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. It is to be understood that this disclosure isnot limited to particular methods, reagents, compounds, compositions orbiological systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein are generally intended as “open” terms (for example, theterm “including” should be interpreted as “including but not limitedto,” the term “having” should be interpreted as “having at least,” theterm “includes” should be interpreted as “includes but is not limitedto,” et cetera). While various compositions, methods, and devices aredescribed in terms of “comprising” various components or steps(interpreted as meaning “including, but not limited to”), thecompositions, methods, and devices can also “consist essentially of” or“consist of” the various components and steps, and such terminologyshould be interpreted as defining essentially closed-member groups.

In addition, even if a specific number is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (for example, the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,et cetera” is used, in general such a construction is intended in thesense one having skill in the art would understand the convention (forexample, “a system having at least one of A, B, and C” would include butnot be limited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, et cetera). In those instances where a convention analogous to“at least one of A, B, or C, et cetera” is used, in general such aconstruction is intended in the sense one having skill in the art wouldunderstand the convention (for example, “a system having at least one ofA, B, or C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, et cetera). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, sample embodiments, or drawings, should be understood tocontemplate the possibilities of including one of the terms, either ofthe terms, or both terms. For example, the phrase “A or B” will beunderstood to include the possibilities of “A” or “B” or “A and B.”

In addition, where features of the disclosure are described in terms ofMarkush groups, those skilled in the art will recognize that thedisclosure is also thereby described in terms of any individual memberor subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, et cetera. As a non-limiting example, each range discussedherein can be readily broken down into a lower third, middle third andupper third, et cetera. As will also be understood by one skilled in theart all language such as “up to,” “at least,” and the like include thenumber recited and refer to ranges that can be subsequently broken downinto subranges as discussed above. Finally, as will be understood by oneskilled in the art, a range includes each individual member. Thus, forexample, a group having 1-3 cells refers to groups having 1, 2, or 3cells. Similarly, a group having 1-5 cells refers to groups having 1, 2,3, 4, or 5 cells, and so forth.

The term “about,” as used herein, refers to variations in a numericalquantity that can occur, for example, through measuring or handlingprocedures in the real world; through inadvertent error in theseprocedures; through differences in the manufacture, source, or purity ofcompositions or reagents; and the like. Typically, the term “about” asused herein means greater or lesser than the value or range of valuesstated by 1/10 of the stated values, e.g., +10%. The term “about” alsorefers to variations that would be recognized by one skilled in the artas being equivalent so long as such variations do not encompass knownvalues practiced by the prior art. Each value or range of valuespreceded by the term “about” is also intended to encompass theembodiment of the stated absolute value or range of values. Whether ornot modified by the term “about,” quantitative values recited in thepresent disclosure include equivalents to the recited values, e.g.,variations in the numerical quantity of such values that can occur, butwould be recognized to be equivalents by a person skilled in the art.

Various of the above-disclosed and other features and functions, oralternatives thereof, may be combined into many other different systemsor applications. Various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements therein may besubsequently made by those skilled in the art, each of which is alsointended to be encompassed by the disclosed embodiments.

1.-15. (canceled)
 16. A method of tracking an object, the methodcomprising: coupling a fiducial marker assembly to the object, whereinthe fiducial marker assembly comprises a housing defining an interiorcavity, a light emitting semiconductor die disposed in the interiorcavity, and a window joined to the housing to enclose the interiorcavity between the window and the housing, the window configured torefract a plurality of light rays emitted by the light emittingsemiconductor die; detecting, by each of two or more optical sensors, aposition of a light ray of the plurality of light rays; receiving, by aprocessor, the detected position of the light ray from each of the twoor more optical sensors; adjusting, by the processor, the detectedposition of each light ray from each of the two or more optical sensorsbased on a refraction deviation to obtain an adjusted position of eachlight ray; triangulating, by the processor, the location of the lightemitting semiconductor die based on the adjusted position of each lightray; and determining, by the processor, the location of the object basedon a known spatial relationship between the object and the lightemitting semiconductor die.
 17. The method of claim 16, wherein thefiducial marker assembly further comprises a metallized coating forminga hermetic seal at an interface of the window and the housing, whereinthe metallized coating forms a ring extending radially inward from theinterface to cover a portion of the window, and wherein the ring isconfigured to shield a peripheral edge of the window panel from theplurality of light rays.
 18. The method of claim 16, wherein therefraction deviation is based on a known refraction index of the window,a known thickness of the window, and an orientation of the fiducialmarker assembly with respect to each optical sensor.
 19. The method ofclaim 18, further comprising receiving information related to theorientation of the fiducial marker assembly.
 20. The method of claim 16,wherein the light emitting semiconductor die is in electricalcommunication with an anode and a cathode extending through the housing.21. The method of claim 16, wherein the housing defines a first notchconfigured to retain the window, and the window defines a second notchconfigured to secure the fiducial marker assembly within a markersupport.
 22. The method of claim 16, wherein the fiducial markerassembly further comprises a rod supporting the light emittingsemiconductor die thereon proximate the window panel, wherein the rod isconfigured to discharge heat from the light emitting semiconductor die.23. The method of claim 22, wherein a diameter of the light emittingsemiconductor die is greater than or equal to a diameter of the rod. 24.The method of claim 16, wherein the window comprises a light-absorbinglayer affixed on an interior face of the window, the light-absorbinglayer comprising a dark coating configured to absorb reflected lightwithin the interior cavity.
 25. The method of claim 16, wherein thehousing comprises an opaque, substantially cylindrical housing.
 26. Anoptical tracking system comprising: an autoclavable fiducial markerassembly comprising a housing defining an interior cavity, a lightemitting semiconductor die disposed in the interior cavity, and a windowjoined to the housing to enclose the interior cavity between the windowand the housing, the window configured to refract a plurality of lightrays emitted by the light emitting semiconductor die; a tracking devicecomprising at least two optical sensors, each optical sensor configuredto detect a position of a light ray of the plurality of light rays; aprocessor; and a non-transitory, computer-readable medium storinginstructions that, when executed, cause the optical tracking system to:receive the position of each light ray from each optical sensor, shiftthe position of each light ray based on a calculated refractiondeviation, and triangulate the location of the light emittingsemiconductor die based on the shifted position of each light ray. 27.The optical tracking system of claim 26, wherein the fiducial markerassembly further comprises a metallized coating forming a hermetic sealat an interface of the window and the housing, wherein the metallizedcoating forms a ring extending radially inward from the interface tocover a portion of the window, and wherein the ring is configured toshield a peripheral edge of the window panel from the plurality of lightrays.
 28. The optical tracking system of claim 26, wherein therefraction deviation is based on a known refraction index of the window,a known thickness of the window, and an orientation of the fiducialmarker assembly with respect to each optical sensor.
 29. The opticaltracking system of claim 28, wherein the instructions, when executed,further cause the optical tracking system to: receive informationrelated to the orientation of the fiducial marker assembly, andcalculate the refraction deviation based on the known refraction indexof the window, the known thickness of the window, and the orientation ofthe fiducial marker assembly.
 30. The optical tracking system of claim28, wherein the light emitting semiconductor die is in electricalcommunication with an anode and a cathode extending through the housing.31. The optical tracking system of claim 26, wherein the housing definesa first notch configured to retain the window, and the window defines asecond notch configured to secure the fiducial marker assembly within amarker support.
 32. The optical tracking system of claim 26, wherein thefiducial marker assembly further comprises a rod supporting the lightemitting semiconductor die thereon proximate the window panel, whereinthe rod is configured to discharge heat from the light emittingsemiconductor die.
 33. The optical tracking system of claim 32, whereina diameter of the light emitting semiconductor die is greater than orequal to a diameter of the rod.
 34. The optical tracking system of claim26, wherein the window comprises a light-absorbing layer affixed on aninterior face of the window, the light-absorbing layer comprising a darkcoating configured to absorb reflected light within the interior cavity.35. The optical tracking system of claim 26, wherein the housingcomprises an opaque, substantially cylindrical housing.
 36. An opticaltracking system comprising: an autoclavable fiducial marker assemblycomprising: a housing defining an interior cavity, a light emittingsemiconductor die disposed in the interior cavity, a window joined tothe housing to enclose the interior cavity between the window and thehousing, the window configured to refract a plurality of light raysemitted by the light emitting semiconductor die, and a metallizedcoating formed as a ring at an interface between the window and thehousing, wherein the metallized coating extends radially inward from theinterface to cover a portion of the window, thereby shielding aperipheral edge of the window panel from the plurality of light rays,and a dark coating affixed on an interior face of the window, the darkcoating configured to absorb reflected light within the interior cavity;a tracking device comprising at least two optical sensors, each opticalsensor configured to detect a position of a light ray of the pluralityof light rays; a processor configured to: receive the position of eachlight ray from each optical sensor, receive information related to anorientation of the fiducial marker assembly, calculate a refractiondeviation based on a known refraction index of the window, a knownthickness of the window, and the information related to the orientationof the fiducial marker assembly, shift the position of each light raybased on the calculated refraction deviation, and triangulate thelocation of the light emitting semiconductor die based on the shiftedposition of each light ray.